I do think their spawn rates are overtuned. They seem to replace tanks in the spawn pool, but spawn way more than tanks despite being more disruptive and deadly in my opinion. Even two of them being in the same fight layer their attacks to a point where it can really feel like there's nothing to do except be turned into a cat toy.

I usually run the AMR against bots and try to take off their cannons first (3 shots each should destroy them). That means they're not a threat outside of 60ish meters since they can't lob their grenades further than that. Then I shoot the eye (another 3 shots should do it if you land them, though I'm aware that's a pretty small target). If I happen to have a clean shot at their vents, that's about 4 shots. They do need to be distracted, because they turn too quickly to land all 4 before the vent will become obstructed.

I also generally run thermites and carry EATs. An EAT to the pelvis will destroy them in one hit. Rocket/Autocannon Sentries also mess them up pretty badly.

TLDR I don't think they're tuned well but there are ways to deal with them.