It looks like you're new here. If you want to get involved, click one of these buttons!
There have been several complaints on this board about "unresponsive" combat in GW2, and like many of you who aren't experiencing that problem, I was baffled by this criticism. I assumed there was some strange lag or performance issue those people must be having that I don't. In response to those posts, many people asked for the critics to post their system specs because it seemed to be something wrong on their end.
So I didn't think much about it beyond some client side issue until I was reading a post on another forum comparing combat in GW2 to WoW and they mentioned that in WoW the damage is subtracted instantly when you executed your skill whereas in GW2 it is subtracted at the end of the animation. Then it occurred to me, this isn't an issue of responsiveness but instead one of instant gratification (not using the term derogatorily, but that's just the best way to describe it).
In WoW, many of the skills are instant cast, and when you press the key to execute those skills you get instant feedback that the skill did damage (regardless of what the animation is doing), whereas in GW2 when you press the key to execute your skills there's an animation associated with it and the skill doesn't actually land until it visually connects with the target. So there's a delay between when you start the skill and when you get that feedback of it doing damage.
However, there's a major drawback to the WoW system. In order to balance that instant gratification responsiveness, they had to interject a false delay between successive skills... the global cooldown (GCD). GW2 does not use a GCD system but instead each skill has a cast time, even if it's very brief. So what's happening in the two systems is this: for WoW you get key press, damage, delay... key press, damage, delay; but for GW2 you get key press, delay, damage... key press, delay, damage.
That's why people feel GW2 is unresponsive.