I'm an Australian HotS Masters League Player, I've been playing since the Technical Alpha. Previous to HotS I was also a Diamond player in LoL since season 1.
I also run a YouTube channel, so if you're interested in daily high ranked HotS gameplay, guides and discussion be sure to check it out. I also actively reply to comments on YouTube and Tweets, so if you have any questions that's the best place to ask them!
Reaching through Time is a must, huge range increase, makes it easier for you to push, poke and siege while being incredibly safe. Time Out can be good, but you should have Time Trap and your long range to protect you. Against heroes like Tracer and Zeratul, someone who can get close to you and kill you quickly, Bye Bye! and Time Out are very good options to get out quickly or survive the burst.
Shifting Sand has the most potential, but Quantum Overdrive is very powerful also at the start of a teamfight and if you can't land your Sand Blast. Fast Forward is not bad, but it's a little hard to get consistently and the increase ability power from Shifting Sand gives us more burst, which is generally more powerful that the slight CD reduction and will end up doing more damage than Fast Forward does anyway.
If you picked up Slowing Sands I still wouldn't recommend Pocket of Time, at level 19 Chromie has enough inbuilt MPS to sustain Slowing Sands, and the extra slow % isn't going to be a big game changer. Loophole has a lot of pros and cons, it'll entirely depend on the enemy team comp and how you want to use your Temporal Loop. Past and Future Me is a pretty solid talent, it's just more damage, can't really go wrong. Andorhal Anomaly is a very interesting and strong talent also, having multiple Time Traps down means you can be very safe, set up ganks/combos and have strong vision control. While maybe not a big in your face game changer it'll be very effective as you use it to save yourself from deep enemy dives or catch someone running away or sneaking around in bushes. Past and Future Me + Andorhal Anomaly are your go to options for level 19.
With Chromie you want to be playing at very safe ranges, being hidden around corners and deep in your backline is not a bad place to be. You'll want to be poking with Dragon's Breath and Sand Blast, preferabbly Dragon's Breath though as it can also be used to siege & clear the minion wave, this is why we pick up a lot of talents based around Dragon's Breath.
In the Early Game focus on surviving, you have poor escape tools and not many ways to get people off you once the fight begins, you're also squishier than melted butter. Clear waves with Dragon's Breath and auto attacks, use your Time Trap in lane as bait/poke tools or use them in bushes to protect yourself from ganks.
When Teamfights start happening look to do as much damage as possible while being incredibly safe. Save your Temporal Loop for enemies diving onto you to send them back, or if you're pressing use it to grab stragglers to set up a kill combo. People will start running into your Time Trap left right and centre, be ready to land your Dragon's Breath + Sand Blast combo to make sure they don't come back. Also use Slowing Sands or Temporal Loop if necessary to secure the kill and really lock them down.
Late game is where Chromie is going to have a good but also bad time depending on the situation. At this point you have really high range but this also means not many allies will be near you to peel in most cases. Because of this you know have to use your Time Trap as mines in a way, stand near them and make opponents come to you, if they do you score some big damage and hopefully an ally can help you out. Continue to harass with Sand Blast & Dragon's Breath but don't rush things, play it slow and siege them down, no one can match Chromie long range pokes and siege.
All these builds I'd consider viable for Chromie, all with different pros and cons.
This is the build I've been going with recently on Chromie. It covers a lot of her cons and deals well with people trying to dive you. The biggest weakness of the build is you're missing some of that 1 shot potential, but it's the most consistent Chromie build and that's what is most important. Deep Breathing and Compounding Aether are interchangeable, depends on what map/heroes you're vsing. I'm leaning more and more towards Compounding Aether though, as you improve with the character it's much easier to gain stacks, it's also not reliant on your getting Mobius Loop.
If you were forced to pick talents before the game begin this would be your build. It's well balanced, tackles everything the meta can throw at you and has some decent team utility. It lacks some of the damage of the other builds but it has added defence, a must have in assassin heavy games. It also sieges incredibly well while being really safe.
This will require a bit of coordination and CC by your team, and even then it might be better to use the Sand Blaster or Dragon's Breath. The focus on massive, in your face damage is something that not many characters can handle. Great for roaming as Chromie, or if your team is looking to try and force fights and win them in a single stun.
Quickly becoming my favourite build, it's safe, consistent and is just fun to play. You lose a little bit of team utility and burst, but you make up for it with a spammable skillshot that will be very hard to dodge and is now able to pierce, allowing for cool combos. If Dragon's Breath isn't working out for your I highly recommend this build. I can also see Slowing Sands working in this build, both are viable.
Fully theoretical build, the idea of using Chromie as a split pushing machine. Bronze Talons gives us more AA damage + increase AA range, very important for killing towers + poking in lane. Mobius Loop so we can clear waves + towers out quickly. The talent that sells it though it Bye Bye!, this allows you to get out of any situation almost instantly, works nearly like a teleport except even quicker. The rest of the talents you can pick whatever you want, the three above though are core.
Medivh Patch - Chromie got some sligt buffs prior to this patch and it helped her immensely. She is still relivetely weak though, but as you spend more time with her and your allies learn how she plays she'll get better. There's some talk of regeneration changes to the game, this can be a game changer for her since a nerf to regen will make her really strong, but a buff to regen will mean we'll need to rely even more on wombo combo.
Release - added a bunch of stuff throughout the following weeks. I'll also keep this bit up to date now.