The lack of people playing Epic levels isn't because the Epic Level Play is harder. It's actually reasonable now with the difficulty levels that MOTU introduced than the former single Epic difficulty.
The reason there is a lack of players at Epic level is because (and I'll be frank) the new Epic quests SUCK! There's been a total of maybe 3 good quests released since MOTU. That's a major problem right there. Not to mention that outside of graphics, the paid portion of the Shadowfell "expansion" was horrible and the Devs refused to changing or add anything to it to make it worth its value.
On top of that, you have the Devs actively making the game less desirable to run. There was no reason to mess with the Secret Doors mechanism. The changes to Posion/Disease were unnecessary. The refusal to make decent Capstones. These are just a few things that hurt the game overall from a player's persepective, but they are even more noticable in the Epic levels.