At 31, I have never been criticized for using any of the pure damage spells or chain spells that cause knock-back. like. ever. In a group, after I place DoTs, I cast them, repeatedly.
Sandblaster, on the other hand....
In group PvE, I use the pet as another DoT and I use Water because he's ranged and won't get in the Tank's way, and I can make sure he's not pulling any aggro he's not supposed to. I've had too much confusion in groups with other pets.
Solo PvE I do use the pet as a tank of course, but in a group situation, you have a tank, so you don't need your pet for aggro unless you need him to pull a stray mob off your cleric while the tank is occupied.
I hadn't considered using crit stones to buff the pet, but that is an awesome idea. Definitely worth a try.