My 116 shadowknight, who is the group's puller, is getting about 1/3 the xp per kill than the rest of my group, most of whom are 117. They are all running 50% to AA, 50% to regular xp but the xp per kill difference is astounding. This was definitively measured in Shadow Valley, and I believe it applied in Maiden's Eye as well, but I didn't measure it there.