Originally posted by Elidrin:

Seriously go kill Yag, continue playing and see if your complaint is valid.

Content isn't finished beyond Yagluth so we don't know how hard the game will be, only that the unbalanced unfinished endgame we currently have does get a bit harder after killing Yagluth. Once higher tier gear is in the game, gameplay after Yagluth might become just another small step up like after the Elder, Bonemass and Moder. The part of the game that has had the most balance passes is progression up to Yagluth, not after.