Can anyone confirm that you get less XP for kills on higher level mobs (IE, 2-4 levels higher then yourself)? Sure seems like it.
There's no reason to believe that is occuring. I haven't quite figured out how the XP system works, sometimes I kill a centaur get 7xp, then I might kill another 10ft away and get 7xp plus a bonus of 14xp. But I've never seen XP get any lower at higher levels, it seems to scale in proportion to your level and the area you're fighting in.