Well you can get a very good MR with undead, and other fatigueles commanders.
Lead Shield, MR amulet, Rainbow Armor, Astral Cap, that's +12 right? Quite commonly used items.
I used all that once on a siege golem, seemed like a really good idea until I realized he had no arm slots.
But still, he was able to soak up a nice deal of damage. I think a siege golem would be a pretty good and widely used summon if he had arms.