Lol jap. I'm pretty sure there will be plenty of creepy people in the game.
If the heroes level then I can personally say I wouldn't want to see an abundance of creeps, that was one of the major problems with Warcraft3 multiplayer. Many people disliked the hero's because it became a, whoever rushes creeps fastest match. I think it can be done properly, and the MMO portion may be different due to the experience cap, but a handful of creeps would most likely be better than an army. And by army I mean the amount present in Warcraft 3 maps.
Bandits here, strong creatures there, it could be interesting, but then why not leave it to just your heroes experience combating enemy troops instead of wild wood land creatures or bandits. Still, as I said it could be done properly. I wouldn't mind it, but I also don't think creeps are all that necessary.