At 28 points per model, they're not terribly costed. They're nowhere near as bad as they were in their previous iterations. However that doesn't mean they're great either.
With a small maximum squad size of 3, and rather underwhelming weaponry, they just don't do very much. You can't take them in high enough numbers to accomplish a lot. Not to mention the models are expensive finecast, so most people simply don't own more than a couple (if even that).
I get the impression that what GW was going for was a punching bag suicide unit, that punishes the enemy for fighting them in melee with acid blood and volatile death explosions. It's a bit of a niche unit design, and isn't really a role that needs filling. There's already the Caustic Blood stratagem which you can put on big gaunt units if you really want to punish someone in this manner.
They're short ranged so need a deployment mechanism to get up the field. Strategic Reserves is a good option, as since they are 1PL per model you can reserve a full 3x3 squads for 1CP.
Taken as cheap single model infantry units, they could potentially take the place of lictors as scrambler deployers, as they cost a bit less. Except for the strategic reserve CP cost, and lack of any of the other useful roles that lictors occasionally perform (namely overwatch removal and pheromone trail).
Their 10" range flamer means they have gone from being one of the few units in the game that had a flamer range long enough to fire from deepstrike, to having a below average range flamer. Due to most other flamers in the game getting a range increase from 8" to 12". Which is slightly disappointing, but not really a big deal.