Holding right click for three straight seconds - character doesn't block.
Bash a target directly in my face - doesn't interrupt
Press skill button - skill either starts the anim then cancels, or just doesn't cast at all. (Including self-cast skills or AoEs that don't require a target.)
Use taunt - Animation and sound effects play like normal, but the target isn't taunted/debuffed.
Press weapon swap then use a skill - bar didn't switch and I just recast some 5k mag skill I didn't need/want.
Heavy attacks cancel while holding the attack button.
Use a root skill on a fresh group of mobs - no root. (Skills like Shattering Prison will literally root one person and not the guy standing an inch to his left, or a target way off to the side and not the guy right in front of me.)
Consecutive light attacks often cause sounds, damage, skill queue, and subsequent light attacks to lag by about a second, making any sort of consistent rotation impossible.
Consistent 100ms ping and 50-60 FPS. No noticeable lag spikes.
It's really hard to enjoy the game when even the most basic, necessary mechanics don't work 50% of the time.