I see this kind of laggy behavior only when on a very crowded zone attempting a very over subscribed FATE. Usually I cannot even see the rest of the players, or mobs, and targeting is useless. I can't tell if my skills are chaining, because so many times the target is gone before GCD let's me attack again.

I don't think this qualifies as a bug when it only happens when a ridiculously large number of players are attempting the exact same FATE or the zone I am in is so busy that everywhere you turn there are players. All the issues mentioned diminish greatly or disappear when running an instanced fight/dungeon or a FATE in a quiet area.