Here's a link to me griping about the crap performance of this game 2 months ago:
http://www.mmorpg.com/discussion2.cfm/post/6205443#6205443
I had installed the game on a big but modern(2013) 7200 RPM platter hard drive on a machine that can pretty much run any modern game on max at 1080P with pretty good frame rates. On that drive or any.
But with MH, I was having game breaking pauses in gameplay, sometimes over a second where the screen became wallpaper. In an action based game like this one, that makes it all but unplayable. Even more ridiculous considering that this was happening in low populated areas, and with few draws going on onscreen. And on a game that uses like 1 gig of memory where I had 8gigs and a 69X OC'd radeon vid card! What the crap???
I tried all the stuff on the forums, changing settings to the ini that would help but wasn't enough. Then to find those settings got reset after every update.
My findings: This issue seems to be largely drive access related. I uninstalled some stuff and made room on my SSD drive to install it there. Frame rates are now strong in even the boss fights in the game, just from going from a platter to an SSD drive.
It's annoying that I have to say this, but that's forums for ya:
Not saying people who don't have SSD's deserve crappy performance(it certainly wasn't in sys req's). Nor am I saying that people who don't have issues on normal platter drives are lying. All I'm saying is that moving this game to an SSD made more of a difference for me than any processor or memory change or ini file change could ever make...
If you want to play this game but performance was killing it for you(as it was for me), and you have an SSD, give it a shot.
TL;DR: I uninstalled from a platter drive and reinstalled to a solid state drive. The hitching is gone.