Soldiers are very useful to block melee characters, help give their allies CA and keep defenders busy, but never have more than 2-3 in a fight. They only serve to make fights take way too long, as they do not offer enough DPR to put the characters into significant danger while their defences are higher.
Now that's solid advice. I might need to get better at reskinning though. I have MM1 and 2 but it's still hard to find the monster I want. I do know how to quickly level up or down a given monster.