I’ve never seen a single end game build focused on it, and it has some massive downsides :
elemental damage converted into chaos damage, but chaos damage has no DoT so the DoT damage would need itemized for as well (most elemental damage skills have a dot component).
-50 HP/s regen (which is actually higher, -65/s on the mythical version, though the mythical version has the possibly more useful acid -> vitality conversion in addition).
The actual stats on it also aren’t particularly mindblowing - they’re not awful, but not worth using without a decent active.
I don’t remember if anyone came up with anything impressive with elemental to chaos conversion before or after AoM, but acid to vitality can have some use
It has its uses, like making phantasmal blades (almost, stupid pierce) vit/chaos or bloody pox full vit/decay. And don’t forget converting the acid spray proc, quite useful for a vit build, or changing tainted eruption to a vit decay nuke (biggest one you can get in the game too).