better without the tin man and the warhead ?

Nah, it's better with them. They're pretty cool and funny as well.

I can't imagine the film being any less silly and over-the-top without Colossus and Teenage Warhead. They were clearly meant to come from a more grounded and serious world - the only thing they did "wrong" was find themselves in Deadpool's madness.

So take these two X-Men away, and Deadpool would still be Deadpool. The juxtaposition with Deadpool and their characters is what makes their scenes so funny and great.

"the realness of a guy sick with cancer turned into a immortal, is a cool story"

I don't know many who would claim that story to be realistic. It's never happened to me anyhow :p

Deadpool is cartoonish. You can't Dark Knight it.