Just some back of the envelope math:

Let's say epic gives a conservative 5 times the xp/min of heroics. Now compare 3.8M to 8M xp required. Without even considering that epic past lives are stronger we get epics ahead by a factor of about 2. Now consider that the xp ratio given includes a lot of fast normal repeats in epics. Introduce reaper difficulty and epics are slowed more than heroics and the severely limited content in epics and no first time resets. I think a bonus of x2 for reaper xp in epics is about right to make it comparable.

I play mostly in heroics, so don't really have a horse in this race... But I think epics needs a basic boost. Even with this boost most people would stick to heroics to double up, but come on throw the people in epics a bone.

Even better double the skull scaling in epics.