In current endgame, acid builds on acid masteries, acid devotions and acid gear do not fare as well as competition. That’s because all of the aforementioned lack (expect the phys res on occultist) the cornerstone defensive stats: phys res and cc res (and also normal res outside acid res). More about it in the specific context of two items:
Murmur’s Kiss is a belt-o with no +1 and no resistances. No, just no.
Venomspine Grieves don’t look bad. They got good da, a nice proc and (seemingly) lots of resistances. It is only when you look at what they don’t have you realize how bad they are.
In current endgame, trashmobs got phys rr, about 40% hero (I looked at 30) and even many champion mobs got stun, just about anything got slow. Boots without phys res and/or cc res are already trash unless they really make up for it. VG are supposed to make make up for it with resistances. But do they? Acid res is almost never needed so they got 2 lines of useful res - big pierce and small elemental - nothing out of ordinary. Furthermore, they got the lowest armor possible for purple boots (lower than aether caster boots Wraithwalkers with both phys res and cc res), low run speed and half-assed %damage.
Why should they be buffed with phys/cc res, though? Is it because acid doesn’t have any? This is where the Anti-Feedback Militia brings up the big guns: VARIETY, DIVERSITY! If all damage types got the same things, it would make the game MONOTONOUS! However, if you play some builds, you notice the following: acid doesn’t really have anything very special about it. Its forte was supposed to be lots of offensive procs and DoTs. But those procs aren’t any stronger (plus acid masteries got no proc machine skills unlike lightning shaman/inquisitor or fire demo). DoTs aren’t much better than, say, demo’s burn. %dmg or wpn dmg on acid builds isn’t any higher then on cold/fire/lightning. So what does the acid have to help it bear literally zero phys res and cc res on all its non-set gear (save the blue boots with stun res that are crap for non-retal, and of the Cabal rare affix that got - surprise - no other res but acid)?
So, considering this, I suggest throwing in one or the other. Phys res or stun/slow res. Preferably the latter as occultist builds aren’t that starved for phys res. Or both. Why not? Why acid shouldn’t have its own Amatoks or Wraithwalkers?