Well, this is old history stuff. The isolated orcs would be the ones who keep themselves away from the modern world, whereas the other orcs are more willing to try to live peacefully. To that end they would be the types who disguise themselves and stuff, but they've also been doing this for quite some time. Thus the orcs are pretty good at keeping up the masquerade, but with continual breeding between orcs and humans, orcs will be phased out.
The epic fantasy feel is just so that the orcs have more depth then "pig people who live in the mountains who don't like humans except for some". After all its not like these fantasy races have only been around recently. I'm sure they have some history behind them comparable to human history.
I mean, what about things like Youkai or demons? Surely they'd have a history too. Had problems with other races, got caught up with humans, and have some reason to hide themselves.