Tryndameres Ult As BIG AOE Zone for his whole team + Heal at the end - CHECK!
It states ALL units, so it effectively prolongs the teamfight, then creates a bloodbath after it heals.
Q: Kalsitas passive - CHECK!
It does say that it will have a short cooldown at Rank 5, but by that time it's mid-game, so it's less of a problem. I like to think of it as Vayne's Q rather than Kal's passive.
Passive: Infinite stacking AD - CHECK!
Firstly, it doesn't say what type of buff it is, for all we know, it could be ap. Second, if it's too OP I'm sure it'll be nerfed. A champion release is a big deal, so Rito will be all over the issues (hopefully).
3-Stack-%MaxHP Damage - CHECK!
It isn't as bad as Vayne's passive, since it has a cooldown. In fact, the fact that there is a cooldown makes this considerably less powerful.
Now, I'm not saying the new champ will or won't be OP, I'm just pointing out that there are rather large assumptions and implications that have no base in this post.