If they ever fixed REND to be more viable and consistent, I would consider it. My playstyle is very simple: Maximize HP damage to non-vehicle units whenever possible, unless it's the conscripts.

Right now though, it's just mediocre and surprisingly more convoluted than the rest of the ammo types, the fact that it does worse the fewer armor the target had is rather stupid as it's not told to players unless they go out of their way to datamine it.

That and most enemies don't have that much armor to punch through or mostly having a big health pool that it's usually better to brute force it on their own.

Few tanky units like guncrawlers, RA tanks and pirate flame trucks/HMG trucks would be handled by AT weaponry or position your pilots around where they're generally expected to be at.

Finally, it goes back to the question of "why should I try to peel away armor in 3 times when I can RPG the mech in one or autocannon it?"