Had this situation come up in a game and had a bit of a revelation. Math seems to check out as well.

I run two blocks of 4 obliterators, one as Undivided and one as Nurgle. Nurgle gives me flexibility to drop them more dangerously and still conceal them with Dark Obscuration.

Had a situation where I was firing them into a 10-man brick of Hellblasters. Rolled well on the shots, but with Profane Zeal, hitting on 4s (indirect), re-rolling 1s, 5-6 Sustain, wounding on 2s re-rolling ones. Wiped the squad easily in one volley. Got me to thinking, depending on the target, re-rolling ones is really all you need. The 5-6 sustain LO from Nurgle (or 5-6 Lethal Skinshift revive from Tzeentch) will almost always be better firing into standard infantry.

Against vehicles the full re-rolls are better, having the 3/4 to wound vs the 2 (depending on vehicle toughness), but into baseline marine bodies, think it's always worth taking one as Nurgle or Tzeentch. The sustained hits especially were absolutely monstrous. 30 hits in a single round of shooting vs a decent sized infantry block.