After experimenting with this, I suggest changing it to a % chance on attack proc.
As a primary attack, it was very underwhelming. It drains energy very very quickly and is fairly mediocre damage. I also further experimented with the Mythical Blood Orb for 100% acid -> vit @ +2k% vit. (doubling the stream damage, essentially)
Upon a little googling, I saw that a few builds had attempted to use this and had seen similar results with acid stream.
There are probably a number of gimicky items that might see more interest/use with a change to %chance to proc instead of mana/use, even if that %proc is low. The argument would be similar to the one here for Acid purge.
If the problem is high energy cost and low damage, then surely the best course of action would be to reduce the energy cost and increase the damage. Changing the skill entirely and leaving vitality entirely without a “spammable” component skill seems…less than ideal.
Here’s a build that makes use of it from a few updates ago. The insane energy cost does mean it has to make some sacrifices (like going Eye of the Storm) but it seems to work well enough for MC.
I’ll suggest that with the full set (dark one’s), the Mythical Morgul’s pistol does similar single target damage to the Acid purge most of the time.
Acid purge is of extremely limited benefit, except for the poison dot stack with pox and +25% crit, . The last bit is nice, but the +25% crit doesn’t kick in a tremendous amount on the big stuff with only 3k OA and a very short burst duration.
And even with that particular build’s 1/3 energy savings, purge would drain energy amazingly fast. (As a comparison, my test build had 20% more energy and only 10% savings)
Without CD reduction, purge is also limited to ~3/second . Wpn damage + dead god is ~2.5/s.
I don’t think it should be a channeled spell IMO, but I could be wrong.
Chances are, with a vit spam caster, you’re gonna take the cabalist. And unless you DRAMATICALLY reduce the energy cost, it’s not going to be usable by a long shot.
Ditto for increased damage - it’s too low. You’d have to substantiate this quite a bit.
It’s bad as a channeled spell because huge chunk of it is dot damage. Had the swapped flat damage and dot damage it would make sense, maybe added bit more weapon damage so it can leech energy more effectively. I have tested it on my poison WH and it was very underwhelming when compared to Biting Blades.