Best Ways to Take Them Out Quickly
I personally believe that they are a little overtuned at the moment, but the best ways I have seen to kill them “quickly” is either using a shotgun to the bottom part of the tail, 4 railgun shots to the head, 4 shots to the tail with the autocannon, or 2-3 rockets with the recoiless rile or disposeable rocket launcher to the head.
I have also heard the flamethrower is decent as well for taking them out but I have not tried it personally. All the stuff above is what I have personally found to work but I feel they take WAY too many hits to take down especially when, like you said, have more than 2 chasing you.
Good luck out there!