from newest release notes:

NEW - Epic Normal favor is the same as Epic before the update. Epic Hard now gives +1 favor and Epic Elite gives +2 favor compared to Epic Normal. Epic Casual gives half Epic Normal favor.
-Epic used to give the same favor as Heroic Elite
-Epic Normal now gives the same favor as Heroic Normal (tested many times)

So, either epic favor is bugged or the release notes are wrong.