None of the bolds lose to rocks and at +2, rotom h ( the one who takes the most from rocks) survives a close combat and ko's back with volt switch or overheat. At +0, it's only a 1.8% chance to 3hko, and usually pinsir isn't going to want to throw around CCs, for fear of the defense drop, so it can almost have a guaranteed safe switch in. If you switch. In as it boosts, there is a very slim chance that you'll be ohkoed, but a better chance that pinsir loses. Also, mega mane makes his life difficult by keeping up momentum and seriously denting, If not ko-ing it. Plus, since we're discussing rocks, let's not forget that pinsir loses 1/2 it's hp upon a switch in with rocks up. This can prevent it from becoming the monster you speak of quite easily. You need some serious hazard support for it to work, which sacrifices momentum. You have magic bounce, but 3 of 5 bouncers aren't available, since you are running pinsir as your mega. So, it's not the beast you seem to think, imo.I feel like it needs to be pointed out almost all of those (including one or two of the Bolds!) lose 100% of the time after rocks and an SD. Neither of those are particularly unrealistic conditions, either, as rocks are, well, rocks, and Pinsir forces out quite a bit even neutrally.
Edit: don't get me wrong, it's a monster, for sure, but it's just not this unstoppable force that will destroy your entire team with 0 support.