Give it to 21 Wiz/Sorc for free.
Reasoning:
- EDK is basically a 1x/day beefed up version of Gate, which makes the expenditure of an epic feat slot for it extremely difficult to justify.
- there's a considerable amount of IG content tied to this feat - be it shrines or stream books. It's sad to see so much work go to waste on a feat that virtually nobody uses.
- Wiz/Sorc could use any help they can get right now and this would be a very minor buff (Pale masters already get EDK for free and it doesn't cause any balance issues).
- it's somewhat bugged by not being able to attack anything with larger than medium sized hit box anyway - an issue that went unadressed for 6 years now, presenting another strong argument against expending an epic feat slot on this.