Frontstab - Epic Enchant
Your backstab no longer requires you to be behind your target.
This opens up Elemental Assassin & Echoing Power to make a great shock tank.
I feel like this lines up pretty well with the power level of other epic RE's and fits the theme of helping synergize your LRE and ERE's to make a small kit. I would love to see this in the game. I think there is a chance you would have to reduce the damage of backstab but don't have a sense for that without testing numbers.
@Rubis Reducing it from 250% weapon damage to 120% to align with Devastate would be totally acceptable to me.