Watson's an Afghanistan veteran, IIRC. Sure, a medico, but I'm pretty sure he wasn't all behind the lines, and did quite a bit of fighting. And yes, Holmes is supposed to know Bartitsu... which means a combination of boxing, jujitsu, and other random crazy stuff thrown in for good measure. It's perfectly gentlemanly to be extremely capable of killing your opponents when you need to. In modern terms, that does make them Action Heroes.