As we all know to get into a raid instance you have to convert your group into a raid group, This nerfs the exp you get in the raid instance.
Recently while boosting a friend through ZG and AQ I found that if when we're both in the raid instance, I leave group, and re-invite him, we're suddenly in a normal group again, and he is getting 20-30% more exp from a kill.
So in brief
1- Convert group to raid to enter the raid instance.
2- Both get in
3- Leave group
4- Reinvite your lowbie Friend
5- Gain 20-30% more exp a kill.