When we embrace that PvP and PvE need to be balanced differently, then fine. When I'm healing for a 4 player dungeon, the cooldown with Earthgore is NOT too short. I understand the concerns with PvP large groups but don't nerf PvE to fix it. A PvP cooldown of whatever duration PvP'ers want and an (untouched) PvE cooldown would be fine.
The problem isn't so much the cooldown. It's that you can run so many of them in larger groups. Small groups can have a few earthgore and the cooldown keeps it balanced. A 24 man group could have 24 earthgore and even with a 2 minute cooldown (which would destroy it for smaller groups and pve), it would still be strong.
If they are to nerf earthgore, I don't think a longer cooldown will accomplish what you're looking for. It would still be used in large groups, but far less useful in other areas of the game.
Yeah, this is why I'm starting to play on Sotha more and more. Sure, earthgore is still strong there, but without CP they are less likely to survive before you burst them down, especially if debuffed.
No CP is just way more balanced, and less infuriating. Get rid of the stamblades and archers, and it'd be paradise.