To answer a few questions:
First: The cards are in specific spots, though i don't know them, its never random. go to every map and check every single things and don't leave til you do.
Second: large mutants occur as far as i can tell when you combine status effects. we used purple and red and it worked well. just kill a bunch of tall zombies and one of them will drop it.
GT: I R NOEbot (with spaces)
I'll help you and you help me, sound good?