In my last session, the task rolls included 5 difficulty 5's, 3x 3's, and a couple 1's... and the only failure was a difficulty 4. Lots of complications, but no outright failures other than the one difficulty 4.
"Epic difficulty" isn't ... it merely generates some threat.
And, no, no more than one helper per action.
5's just not high enough to be labeled "Epic"... Heroic, sure, but not Epic.