Ran a ToS, dual wield barbarian, sword and shield guardian, all 80, and a 47 assassin through it so far... Barb and guard have almost no aa's at all, one level in decisive and pressing strikes each and are a mix of t1 and t2 gear from world bosses.
Can't say that it's been difficult once I figured out the mitigation debuff. There's no reason to ever be running around with the negative mitigation on you. Did have to kite a couple times with the assassin when I got too many mobs.
Does seem a bit long but that may be better than too short. Does go a lot faster the second time through.
Took longer on the guardian, duh, but not really harder. The surprise to me was that the dual wield barb just steamrolls it.
Can't speak for all classes and all levels of gear but it seems about right to be somewhat of a challenge but without being too difficult to me.