The problem with "Instant OFF GCD" abilities makes combat feel less rewarding.

[BlackShroudMercs]

Each step of an animation in a combo takes longer. My guess: it's obviously on purpose.
Do the first two steps instead of three when you know the boss is about to use an ability you wanna interrupt.
More dmg/aggro= less reaction time, less dmg/aggro = more reaction time

QQ about not enough dmg/aggro if you use just 2 steps of the combo? Figure it out with your team when they need to deal less dmg so you can "wait" to interrupt.

Instant abilities = one can be used after global cooldown abilities
it's a new mechanic
deal with it

Its not instant if it doesn't work the second I press it.

Deal with that...