Quote Originally Posted by Seraphor View Post
That sounds a little too easy and 'hand-holding'. There'd basically be no penalty to improper timing.

One thing they could do, is allow buffs like that to form stacks, but have successive stacks have diminishing returns.
1 stack of Trick attack gives a 10% debuff.
2 stacks of Trick attack give a 15% debuff.

This way, it certainly wouldn't be worth having two Ninja's, but if you did, and their buffs overlapped, it wouldn't be wasted, but there's still incentive to time them apart.
There's nothing handholdy about a system where players are expected to play their class with them being the only example of it, but sometimes being thrust into a system where you have multiple copies of the same class. Savage raids require you to have unique classes across the board, no duplicates, so you're expected to play the class as if no one else is there of the same class.

While I'm not certain buff stacking versus flat duration increases is the correct way to go about it, it's simply a fact that the current system is also not how the game is, strictly speaking, intended to be played.