Druid is weak to combo. OTK Anduin, Quest Mage, and Paladin are all strong against Jade Druid. I also find Murloc Paladin to be hard.
Yeah it's way better than n'zoth. You don't require any setup to cast it. You just vomit your cards to gain massive tempo then point UI at something and do it again.
When I play N'Zoth in the deck I use him in, the game is over. I have played my win condition. UI doesnt do that. It is definitely worth ten mana, and I think it is comparable to N'Zoth.
UI exacerbated what made people hate Jades in the first place. I always argued before that the shuffle option on Jade Idol wasn't nearly as relevant as people said, but now when Druids can draw 10 cards throughout the course of a match it is MUCH more relevant now. Now we start seeing a case to be made to remove the shuffle or capping Jades so they stop growing at some point. Hell UI even made late game Innervates more relevant to give people more ammunition to think that card should be removed.
I think capping Jades at 10/10 is pretty reasonable.
What scares me is that there are SO many varying options on what the problem is, and Blizzard tends to overnerf. I will be really mad if they nerf Jade Idol, UI, Innervate, and Jades all at once. I hope they just change ONE of these, and watch the meta progress. I don't think they will change Jade Idol because it just got a hate card, and that is a solved problem to Blizzard. Innervate and UI are most likely.