Hey folks! It's MardyVain here, Hots player since the last phase of the Beta. This is my first guide so please, feel free to constructively criticize and discuss whathever you want.
As introduction, I have to admit I'm not very into Li Li: I've never played ranked games with this hero so this guide may be non appropriate for that gamestyle; however, this still seems to be atleast fun to play in hotjoin. That been said, let's start!

I've always been a fan of mmropg and rpg in general, in which my favorites classes were always hybrid ones; I loved to damage and heal at the same time, trying to find the perfect balance within these two dimension.
I used others support heroes in Hots, like Brightwing and Malfurion, but I've found that these heroes are better if played right into a pretty purely offensive (rare) or a most defensive (much more common) build.
And then, here she comes Li Li!
The core of this build is the Cloud Serpent ability, making you capable to deal and heal a tons of damage.
First things first; let's take a look at the general pros and cons of this build:

Pros

Very hard to kill.
Can outlast most of the others heroes.
Tons of healing.
Tons of damage.
Late game is your bread and butter.
Can still provide some (quite) nice burst healing.

Cons

Less burst healing potential.
Less CC.
May be a bit slow in the early game.

Fast Feet combined with Blinding Wind is your best way to escape critic situations. However you shouldn't rely too much in this trait during team fights, considering most of the time if you're trying to escape from a bad positioning probably you are already dead.

Healing Brew is the main basic Li Li's healing skill; spam this in the early game to support your lanemate and to avoid enemies' burst. Not much to say.

Cloud Serpent is where this build shine. Nice damage, nice healing comeback, with this active you can tank most of the heroes out there. Pretty amazing.

Blinding Wind is your main CC skill; the damage is not really astounding, while the blinding effect can still make your enemies' offensive much more sustainable.

TIER 1 TALENTS

At first I was confident using Timeless Creature, but after a few try I found that Conjurer's Pursuit is far superior. This will make your mana pretty endless in the late game, if you played right, thus is not worthing picking a 4 seconds Cloud Serpent boost. However I'll encourage you to try both, to find the best bet for your playstyle.
Pro Toss and Gale Force are just too weaks compared to Conjurer's Pursuit.

TIER 2 TALENTS

The core of the build, hands off the key to balance offensive and defensive capabilities. This allow your Cloud Serpent to heal and deal damage at the same time, restoring health to targeted hero. Let the Serpent rise!
Other talents are not considered, just because this is a must-pick for this build.

TIER 3 TALENTS

Again, another must-pick choice. More bounce mean more damage. More bounce mean more healing. Do you need more reasons to choose this?

HEROIC ABILITIES

The choose here is really up to you. Personally I prefear Jug of 1,000 Cups because it allows you to sustain much more damage and it can really screwed up your opponents if timed well in a team fight, letting your teammates survive a bit more.
Water Dragon is useful to CC enemies down, but I don't think it's really the right choice in this build.
Pick this if you have another support heroe in your team and he/she's going deep in healing build.

TIER 5 TALENTS

Ability power is always good. Spam [Bliding Winds] during teamfights to CC enemies and to stack this. This tier is, however, a little bit more team dependant than the others: nice choice are indeed even [Shrink Ray] and [Elusive Feet]: you can pick one of them if the enemy team got a painful assassin like a morph [Illidan] or [Nova].

TIER 6 TALENTS

Two [Cloud Serpent] at the same time? I'm going to dance!
No, really, pick this and cast Cloud Serpent ONLY on allies; avoid casting it on yourself for whatever reason after level 16 (seems a pretty dumb advice but trust me, it takes a lot of practice to me to understand this).

TIER 7 TALENTS

And again, this tier is up to you. I found Storm Shield being perfectly combined to Jug of 1,000 Cups, as it can refill the health bar almost of the entire team. Kung Fu Hustle is another wonderful talent, and you can considering pick this if you went for the Water Dragon heroic talent.

In the end, this is a very fun build to play. I'm topping damage and healing most of the time (hotjoin only, better to remind that) while I can literally face pretty anyone 1v1. I feel that this build could be less useful in organized team, just because you're wasting much healing and CC's skill to maximize your damage.
This is a strange way to play a support hero, but you should give it a try (if you don't have done it yet, it may be not the first Li Li's build focused on offensive playstyle).
Hope you have fun, folks!