Hi, my name is DaCrazyHun.. I'm a hardcore/average player.In almost any 1v1 situation, you'll have the enemy running which is where Illidan really shines b/c he's designed not to let his enemies get away comfortably.
I'm also a Master Illidan, and I think I play him pretty well in most cases. He's a very situational hero, meaning his talents can change, depending on the team comps.

As most know, a lot happened w/ the new patch that just took place (March 29th 2016) and with it, came the rebuilding and moving of Illidan's talents. Some new talents, some old, some moved to different tiers.
Now I've had about 50 games as Illidan since the patch went live so I feel I have a pretty good grasp of what works and what doesn't at the moment.

This guide is still being developed. It is not 100%, will be kept up-to-date.
Added explanation of *April 4th 16*
Added explanation of Illidan's core abilities *April 6th 16*
After additional testing, readjusted the build/added more info. *April 7th 16*

Dive [Q]
This ability allows you to close the gap between an enemy and yourself. Coupled with , you can use it both defensively and offensively. I like to rely on my teammates to some extent to allow me to dive onto them to get out of tricky and tough situations. This ability is crucial in use, as it allows you to block enemies, slow enemies, and secure kills. If you're not using it a lot, there's a problem.

Sweeping Strikes [W]
This talent is primarily used to catch up to enemies/get away from enemies. It helps close gap on your enemies and if you couple it with , a good portion of the damage will be coming from the AoE. Its great for taking down tanky heroes, or heroes who have shields. Very important ability that needs to be used a lot in order to be efficient.

Evasion [E]
This is probably your most important ability right here. This is Illidan's bread and butter. Its what makes him durable and a threat. The more abilities being used, the shorter the cooldown is for your Evasion. Picking when to use this at the right time is crucial, as if its too early, you will die and your team will be punished for it. If too late, you will find yourself in a disadvantage trying to stay alive.

Working with , timing this is incredibly important as it allows you to reduce damage from the next 2 abilities, which is amazing. Make sure to poke and retreat. Do not just go into the middle of a team fight and start focusing on someone. Illidan can't just stay in the middle of a team fight unless he has a certain comp team that can keep him in the battle for longer periods of time. Otherwise, make sure to poke and retreat. Go back in with your cooldowns, and don't get too far from your healer or screw up the positioning as it will make it harder for your whole team.

Early game is where Illidan is a pretty weak, so being careful is key. Most of the time, Illidan can lane against others, and ultimately in lanes where its both Illidan and an enemy soloing, Illidan will most of the time be able to put out extreme pressure on the enemy and keep them on the defensive. Timing is key for poking and getting back to safety.

Illidan is all about high risk, high payoff, or high punishment. Deciding what to do with him is a challenge cause its always risky.

This is basically the time everyone gets a power up, being their ultimates.
As Illidan, you should primarily focus on the objective, team fights, and camps. B/c of the low cooldowns and heals from your passive, taking siege camps is not a problem. I find that in a lot of games, a lot of people don't really like to depend on camps or do them, which is where I come in. Camps add pressure to the lanes, and ultimately give you more breathing room on what to do.

Pick your team fights properly, try to always stay together or close to one another. As Illidan, killing enemies who try to run away is your specialty. Barely anyone can get away from a good Illidan. Use your ultimate to surprise your enemies and throw them off guard/screw their positioning/targetting up.

This is where the team fights matter the most b/c dying is just that much more of a punishment now.
You have a good amount of survival by now, and if you picked up Bolt of the Storm, you'll have an even better way of getting out of situations safely. Everyone has gotten a power boost by this point, with their lvl20 talents.

Make sure to stay together and not make any clueless plays or moves. Coordinate with your team and push/defend together. Use your team as a distraction to go in and get a kill or do some damage. Most people hate Illidan because he is a huge threat in team fights. He does ALOT of the work, especially now w/ his new and revamped talents.

This is the talent I would say is best.There are just too many benefits of this talent to ignore compared to the other 2.

This helps tremendously in team fights, taking down camps, as well as chasing enemies down.
The reason it beats is b/c it has more uses.

Battered Assault is great if you are facing comps where the enemy team stays bunched up a lot, so getting that Sweeping Strike bonus damage will be a ton easier. But Illidan is the type of hero who can keep the pressure on the enemy until they decide to try to run, which at that point, it becomes a 'catch me if you can' and Illidan should 99% of the time catch the enemy, except if they have a blink or root.

is alright but its not optimal. Seeing as how you get 30 additional damage to your basic attacks, it sounds awesome on paper. However, w/ Immolation the ticks are even higher than 30 and they damage every enemy around you, as opposed to just 1 single target. Not to mention, the Immolation ticks are fast, thus adding more burst to the main target you're attacking as well as still doing damage to anyone else around you.

This is something that I find to be way too crucial for Illidan's poke and survival sake.
I've used to save myself so many times, its ridiculous how effective it is.

What it does is increase your dive & allow you to use it on teammates as well. Having this extra dive range is the difference in a lot of cases between letting an enemy go or securing the kill. It allows yourself a greater chance basically, to catch your enemies and get the kill.

Now if you're getting pressured too hard and an ally is nearby? Dive to them > Sweeping Strikes away.
Want to catch an enemy off guard and go in to attack a bit? Dive a teammate near an enemy, and Sweeping Strike to the enemy. Even in situations where I was pushing a lane with 1 other person, and I happen to get ganked by all 5 enemies, the ability to jump to a teammate is so handy, it will be crucial in getting out of tricky and risky situations like ganks and what not.

and are decent picks but again are situational and I find Friend or Foe to be too helpful to pass up. Besides, Illidan, with his extra ranged dives, is able to keep up with almost any enemy, so the movement speed would be sort of a limitation considering you can already keep up with enemies and with Friend or Foe, you can also have a way of getting out of risky fights.
Why go for movement speed when that isn't an issue? I'd rather have an option of getting out of sticky situations. I can't stress how many times this talent has saved my life.

What I love is Friend or Foe is great both offensively and defensively.

is the go-to pick for lvl7. Hunter's Onslaught isn't bad either, however most of the damage comes from the basic auto attacks, and they grant more health back as well, b/c not only is the health recovery doubled nearly, but it also occurs very fast b/c your attacking very fast.

Previously believed Hunter's Onslaught was superior, but after being advised differently, and doing some additional testing, its clear that Thirsting Blade is the better of the 2.
They're both decent picks, but I definitely see better outcome w/ Thirsting Blade.

Nothing really changed except its Lvl20 talent got modified a little.
Very handy pick. Can be very rewarding as well as risky. Use it to go in for a kill, or to get out of a team fight fast. I love this ultimate so much.

is great for its AoE. I usually grab it for the comps where team fights are longer than usual or maps are smaller. If you do grab this, make sure you grab the lvl20 upgrade for it.

Not only does it evade basic attacks but now Evasion grands reduced ability damage, which is crucial for survival in team fights. This is a talent that should most of the time be picked up as it can be the difference between life and death.

I'd like to think this is the best talent at the moment in this tier because coupled with Illidan's attack speed, you are hitting someone for quite a bit.

is very good, but it depends how and when you use it. Using it too early or too late yields minimal results. Couple it with Lt Morales's SD ultimate, you are an insane threat to the enemy team. It can make all the difference in securing a kill or not, but the only con is, you have to build it up to 5, and depending on the situation, you may not always be using it as much as you'd like, which is where ...

comes in. It's a safe ability, allows you to continuously hurt the enemy as long as you are consistently on them. Now the con with this is..the simple fact, you may have to jump from target to target, and blow enemy ability cooldowns, which in turn will make Fiery Brand not as useful.
I advise you to pick this talent up if you know you will be focusing certain players more than the others, and particularly if you have a very strong aggressive team that pushes the enemy to run away, which is where you come in and chase them down.

All in all, both are very good talents.
I would advise to grab because in most cases, you will have to jump around quite a bit, taking pressure off your teammates and making the enemy think twice about engaging. By doing this, building up to 5 stacks is not hard, because you will be continuously using SS and Dive to push enemies away from attacking or supporting. As soon as you get focused, dive out or switch to a new target. Keep in mind you are squishy so making the right moves at the right time really does matter.

This is usually what I like to grab cause its such a good tool for securing a kill or getting out of a fight. Illidan already has amazing sustain and damage in 1v1s. He is the king in most situations. Therefore I like to sacrifice the extra damage and slows or improved ultimate's for something to help w/ survival.

Illidan moves around a lot, and the general consensus is that when you see an Illidan in any team fight (or any sin for that matter), they are focused cause people know their damage will hurt and if they aren't focused, their teammates will die. So being Illidan, you have to expect to be focused and attacked primarily. But that's what Bolt of the Storm will help with. Not to mention your amazing mobility of diving and sweeping around.

EDIT: This isn't something I advise picking up every time. It really depends. As Illidan, your mobility is your key and getting out of situations with Dive or SS should be good enough. However, there's no harm being safe. I like to grab this if my teams offensive pressure is very strong, and I can sacrifice a damage boost for it, as it just compliments your survival. I also like to grab it when the enemy team has very good amount of CC or stuns, as it has gotten me out of certain death situations, where otherwise I would definitely had died.

It adds to your mobility, and with it, I really don't think anyone should get away from you. It's just so unlikely.

If you grab The Hunt coupled with Blades of Azzinoth or Fiery Brand, your damage will be evident still. Having the option to grab a damage boost @ lvl20, doesn't mean you should always take it. Why go for damage if your lacking in surviving? If you're comfortable with your survival, grab the damage boost.
The upgrade for the Hunt isn't that great so I don't really ever grab it.

has been really beneficial late game, coupled with BoA. The damage is amazing, and the fact most enemies can't get away from you, means that you can stick on them and continue to deal the absurd damage. It's a very handy pick but you have to know when to grab it.

In the end, it really comes down to the enemy comp, your team comp, the map, and how the team fights go. By lvl16-20, you should have a very good grasp of how the team fights go, who to focus, and who to stay by or away from. I don't know how this talent isn't useful. It adds mobility to your hero, it gives you another way to secure kills or get out of sticky situations, and has an overall low CD for the amount of utility.