Mellkor, It absolutely could be balanced, but the Tier and AMP system likely complicate that. Imagine if you could Tier up just your DPS and Tank pet and still had access to the other two: You'd have no problems in PvE at all, just send the pets in and stand back and shoot a little, you'd barely have to try to quest up while the four of your pets went and handled all of the work. It really would eliminate the "active" from the combat. While a cool idea, I think that it would have made the balancing far too dirty/messy for the dev team. Subsequently this simpler system makes for better class balance for the players. Just my two cents.