If they weren't already named by me then I'd say keeping it to one or two (or more if the situation got worse), is fine. Generally if they have a name I gave them they play a role no matter how small. 

They definitely shouldn't be dropping like flies unless shit really hits the fan and the villains right now were just C-Listers anyway.

You can pretty much go all out with injuries though.

EDIT: Hopefully the epic nature of these epic battles of epicness aren't epically ignored. I spent a lot of time writing all that :P