While variation is good, this description gives me the shivers: "a weakling, an average or a champion version", you'll have to expand a bit on that because from where I stand that just means one hits harder/less hard than the others and has more/less hp. I instantly get flashbacks to Fallout 3's Feral Ghoul Reavers when I hear this... (that is *not* a good thing btw ;))
Slight variations in stats I can appreciate but you make it sound like there'd be huge difference, that just ends up being annoying (as above mentioned Reavers).
I'd much prefer if (generic) adversaries have a pool of abilities that make sense and which ones each instance gets varies. As such you know what something *might* be able to do, but you don't exactly know what exactly they are able to do. The bigger the pool the more interesting the combinations possible of course. I guess this would be a lot more work than just cranking up/down the hp/dps of mobs though.
