EXP in a party is very unbalanced, as a mage I seem to get a lot of exp because of my dps output but then the healer does not get much. In a group I think the exp should be even split between the group. Healer main job is to heal us and should not worry about doing dps to get more exp.
In a party where everyone is the same level everyone gets the same exp if they are even barely on the threat table, and at different levels it is still split percentage wise but each will get different based on how much higher the mob is from you