The game mechanics at this time encourage that play in my opinion considering the ability of the pets to far outpace the character in damage.
As an archer, my ability to kill the monsters my pets face are almost inconsequential. I more often then not am firing at a creature that is already dead...it is also very unsatisfactory to be sooooo far behind my own pets in the ability to kill.
If I was doing damage equal to my pets then I most certainly would want to get my character involved.
That's the real problem - the game mechanics. To change this type of play you would have to properly balance the pet/character damage ratio.
In every level of character advancement that I can think of, there is always a pet that can be purchased that far surpasses my own damage.
I do 6K DMG while my pets are doing 100K+...I do feel like pulling out a lawn chair, sitting it down in the dungeon and just marveling at the ability of my trained minions to decimate the waves of monsters before me. Of course, after awhile I might get sleepy.....Roughouse, this is a GM, I'm talking to you...huh?
