Bards and XP???Follow

It seems to me that i found something a little odd, the other day i was in a group of 4 people and we were killing reds and i had horible xp gain while the rest in my group was getting great xp. then the next day i was an 11 bard grouped with a 15 warrior killing blues to him and he was getting about a blue bar every kill and i was getting a fourth of a blue. this seems a little wrong to me seeing how they are much more difficult to me. then i conducted another experiment and found that i get a lot more xp the closer the enemy is to my level. as a 12 killing 13 mobs i get more than a 11 killing 13 mobs, is this a bug or am i missing something. it would seems to me the harder stuff you kill the more xp you should get.