Enchanted reprise as an oGCD

[SaberMaxwell]

If it were an oGCD, it would need to be noticeably less than (20 mana * 6.8 potency/mana), so ~100. At 136 or higher it would be optimal to spend all your mana on E.Reprise. Since it wouldn't delay further spellcasting, its value would only need to account for the mana it spends.

I'm assuming we're talking about a short enough cooldown that it could be used on demand; if it were longer then the potency could be higher.

Any theories as to what cooldown would be good to balance it?

As an on command dump, even having a low potency would be okay although many would view it as discount Edge of Shadow.

[Rongway]

Any theories as to what cooldown would be good to balance it?

As an on command dump, even having a low potency would be okay although many would view it as discount Edge of Shadow.

If its potency were low enough below what the mana would be worth if you spent it on a melee combo instead, then it would be okay on a 1.0s cooldown. You wouldn't use it except as a mana dump prior to Manafication, and in such a case it could be used up to twice to dump the 20|20 that would be lost anyway due to Manafication.

On a longer cooldown it's harder much harder to say.