Something which me and my friend observed today. I'm death and she's myth. This time through we've been doing the quests together, pretty much in lockstep. I've been consistently about 1400 exp or so behind her, so today, when I leveled up to level 69 ahead of her, we were both surprised. Furthermore, I was now allmost 10k exp ahead of her, so somehow I had gained allmost 12K exp on her, allmost overnight.
Upon further investigation, we discovered that for the level 68 spell quest, Death gets 11000 exp for defeating the hoarder, while Myth only gets 1800. Even more investigation indicates that all the other schools too receive 11k exp for defeating the hoarder, its only Myth that is getting the short shift.
Its only a minor annoyance since it will become moot once we both hit level 70, but it seems like it should be fixed.