Even Epic Fantasy skews shorter than you might assume these days.
Pat Rothfuss, and David Anthony Durham turned out some bug-crushers (very, very high quality, well-written bug-crushers both of which I give two hearty thumbs up...)
Compare that to my book, or Shadowbridge by Gregory Frost, or the DnD novels and media tie-ins that are often the gateway drug to Epic/Heroic Fantasy... Not all of these books are long. Some of them are barely longer than novellas.
Heck, you can pick up the original Elric books in their first printings, and they can't be more than 80,000 words a pop. Seriously, I re-read the first one just because I saw it at the library and thought it'd be fun to re-read. It was. It took less than four hours.
This assumption that epic/heroic fantasy books skew long ought to be investigated further before anyone assumes it's true. I suspect, with just glancing at my bookshelf as evidence, that there's a wider spectrum of word-lengths in epic/heroic fantasy, but one that still averages out in the 80,000 word range on the whole.
Still, I wouldn't mind a number-cruncher to prove me wrong. I didn't do anything scientific to reach my result.