Back on the Live servers I had a Mind/Psi permaDom, and I don't think Mind Control needs a true pet. If the set's damage is lacking I think a better option is to just boost the damage of Mesmerize, Dominate, and Levitate. Also, just as a QoL, remove the delay on damage from Levitate. Before i6 it was synched with the moment that an enemy hit the ground, but since they added ragdoll it never synchs properly.
What I think the set could really use is a change so that Interface Incarnate abilities that add DoTs to your attacks don't affect Mesmerize, so taking those abilities doesn't make Mesmerize useless.