Sam, my "boosters" are all level 80's so everything is grey to them. Hence, they can't cause any damage directly as it saps the exp for the "boostee". (This is the entire rationale for using high level boosters with indirect damage like pets or shaman totems.)

Maxion, I just use the mage for convenience. Obviously, I can't group the warlock with the rogue as the warlock is within range and would sap all the exp. I simply use the mage as a dumb group member for the reasons you alluded: porting when needed.

No clue on this anomoly. I'll keep tinkering with it to see if I can find a cause. I'm wondering if there's a certain max distance between group members for this to work. (i.e., if the rogue gets too far from the mage the rogue is then treated as "ungrouped" for exp calculation purposes?)