What causes skill activation lag?

Been playing moderately for over a year now. I mostly play PvE. I frequently have problems with casting/skill activation times being longer than they should. I have a stable internet connection, w/ usually a 200ms ping rate. I normally get about 45 FPS. A quick example: with no other lag problems going on, PvE w/ full party of hero/hench, I'll approach a "large" group (lets say 12) of foes, and try to cast a spell with a 1 sec cast time. I look at my watch, and it just goes off after 4 secs. Seems to happen more often in the more difficult areas of PvE, and not as much with fewer foes.

What causes this? Specifically, what part of the PC is causing the bottleneck, or is it just ANet? I know 200ms ping isn't brilliant, but it's not bad either. The only thing I've noticed is a drop in FPS at the same time.

Any help would be much appreciated, Thanks!

Stellar - this is actually quite a good question (to me anyway). I have noticed the same thing, but always assumed a normal lag issue is responsible for this - I play with a average of 200-300ms.

It's the reason I don't play any PvP at all. Try casting an interrupt (or any other skill for that matter) when it takes 3 or 4 Real Life seconds to activate -.- (I just know that by the time I have caught up with the action, that Sin is dancing on my dead body)

I hope someone can provide an insight into why this activation lag should be.

Since you say the problem is more pronounced with larger groups, as well as being accompanied by a drop in FPS, it may be your graphics card bogging down trying to render all the models and skill animations. Try lowering your graphics settings and see how that works. If that drops your lag, look into upgrading your graphics card.