This may be redundant, and if so, I apologize.
What quests, or quest chains, would you like to see turned into an Epic? What reasons for it?
Mine would have to be Delera's Tomb. I'd like to say that it was for some lofty reason, but it would be really for the epic end reward possibilities. Epic Carnifex, Sparkstriker, or Serpent Branch to name a few for weapons. And the Epic armors and trinkets.
Now, I know there will be naysayers to choices, but this is a purely opinion based topic, so have fun and don't worry what others think...