Earthgore was already nerfed to be almost pointless to run. Healing proc sets are generally useless in pvp, there are few situations in which a proc on healing done is useful compared to stronger survival, resource management/ult generation, or even spell power monster sets aren't more useful. Earthgore's proc at least was better designed than some of the previous healing sets, with a health threshhold trigger (I think chokethorn needs to be redesigned with the same health trigger as earthgore). Earthgore was meta for a long while because it removed all ground effects. That was the reason cyrodiil groups used it, even healers ran it. Once that got nerfed down to one effect, before the healing got reduced, we'd have dps run it as an oh ***, because pretty much any source of healing when below the health threshhold would trigger it, including cp passives and potions and we could control when the earthgore effect went off more in negates. But at this point its barely worth finding a place into a group with much more effective sets like balorgs.
Healers generally want to be running bloodspawn, and dps balorgs, unless you're doing 1vx or very small group play, and even then I see troll kings as a better solution for those situations than earthgore.
Earthgore is just extremely prominent, visual and folks realize its playing an effect, when it really doesn't make a huge difference anymore.
To make it useful again, I'd be fine when them reducing the healing to very little, and having it focused on ground purging effects with a shorter cooldown. Like 7k healing (out of cyrodiil), and 1 ground effect on a 10s cooldown would be a valid set worth choosing.
(Also ZOS really needs to improve the 2% healing done set bonus in general, its utter garbage)