Couple noobs on the boards and a couple in game. Maybe the same. To none it is obvious that mercs work as a group mate to increase your xp.

Perhaps add a room in the academy that explains group bonus xp and also mercs? Maybe even have a level 1 merc with 10 hp or whatever so they can see the affects in the academy.

At they VERY minimum, let's add the merc group experience as a notation in the "help pets" help file!