The other day, a couple friends and I went in, killed goblins, worked our way to giants and killed them (all dark blues where we were).

We all eventually noticed that when we killed goblins, though they seemed lower level, our exp bars (all in AA, at least mine is) moved. Yet when we killed thet Fire giant mobs, we saw no exp change. (We noticed this and then watched it fairly carefully... we could kill ten giants and see no change, then kill a single goblin and see a small incremental change, about what you'd expect from a lowish dark blue.

Has anyone else noticed this?

I have killed the fire giants after clearing from the gobbies and although the xp seemed slightly less if was still moving at its usual pace. I think it was just the giants took a tad longer to kill, making it appear that the exp is not moving. This was all at 100% aa exp too.

I noticed precisely what you are talking about and I /bugged it.

A guild group was working its way from the goblin side, and I was getting about 2% AA exp every three kills with the goblins. Once we reached the giants, which were higher level, the experience bar stopped moving. It didn't budge. At all.

We all noticed it, and at least two of us /bugged it. This was about a week and a half ago and I haven't been back to see if the problem remains....but from what you said, it still seems to exist.