Acid is good against bladelings. I suspect it might be good against shroomlings but I haven't tried.
One thing that would "fix" special ammo is to allow jhp and w2c versions of them, but that doesnt actually make any sense. Shock 5mm would be cool if they stunned enemies on a crit, but as it is, even against robots I think w2c is better unless their DT is just SO HIGH, but then why use 5mm in the first place? Contaminated seems like it's good for sniping some zoner in a chokepoint where other enemies have to move through to get to you. I know that elemental damage on crossbow bolts is multiplied on a crit, so maybe with a critical power anatomical chimera (or other high crit gun), they might be pretty good?
It bothers me that JHP incurs a penalty vs DR/DT and gets a boost after, but w2c penetrates and does the same damage after; shouldn't w2c have less base damage? Like against heavily armored enemies (anti-rifle tacvests, robots, full metal armor, bladelings), you could net more damage, but otherwise they're weaker.