I did something similar but what we did was a friend and I made small 10 fig forces with a hero and we battled cooperatively against another friend who played as a necromancer that kept summoning zombies and whatnot. Worked out well because the heroes had lots of red shirts... Also, our house rule for red shirting is that as long as you're within 6" of of a hero you can die for him. Less dice rolling, more glorious hero moments. Win, win.
"Hey, you try making love to a complete stranger in a hostile, mutant environment, see how you like it."