I have to agree that the mortar team for the soviets is over powered. Mortars on both sides don't nearly have the same amount as punch as the soviet model.
One could argue that the rate of fire is slower, but if you're the type of person that knows how to clog up a player with plenty of conscripts, and don't care for friendly fire, you can really clean house with the conscript/mortar combo.
Secondly, I know the soviets are meant to zergling. Yes, they're very, very easy to suppress but I think their HP/Defense level is a bit to high for being ill equipped and poorly trained.