CTHULHU DARK is an ideal rules-lite horror system. For purely Cthulhu uses I'd stick with players needing to run from mid-level to major beasties, however, for other horror games (along the lines of CHILL), I was wondering about giving monsters varying dice. Something like a zombie from Night Of The Living Dead, I was thinking that their individual die type could be a 4-sider. The odds of a player beating a contested roll with one of them would be better than a cultist (they are very slow and stiff). However, two of these creatures together would be worth a d6 rating, and a swarm could be worth a d8 (treating results of 7 and 8 as a 6).
Greater monsters, say a bog-monster (whatever that might be) would have a d8 challenge rating. Something really big and nasty could even have a d10 or d12 to roll with, and the player's odds of beating these are really slim.
Does this seem like something worth exploring?