This is my first Hero Concept, so expect the wording to be clunky and the numbers to be off. Apologies.
While I get this will never happen, one of the things I love about Heroes of the Storm is how it combines radically different universes together. I thought it would be really cool if the Avatar universe arrived at the nexus! I plan to do a concept for every Element (I'm thinking Zuko, Toph and Aang as Assassin, Tank and Multiclass respectively).
ANYWAY, AS FOR THE ACTUAL HERO:
Katara is meant to be about managing a limited resource- her water supply (mana). She has only brought a limited amount to the battlefield, and though she can reuse it- almost all of her abilities require it! She has to manage this resource carefully- sort of like Sonya with Fury.
Her main damage comes from Water Blast (how does the damage number look?) which is meant to be a slow moving skillshot (the water is in use in mid air, and also while charging it up- think Chromie!). She can Chi Heal two targets, racking up some great healing numbers- but losing access to her CC- or she can forfeit a different strength. Its a juggling act.
Or at least, thats the intention. I've created this at 2A.M, so maybe the hero just dosen't work. I'd love to hear your feedback, since this was a lot of fun to make but I'm really clueless about game design