There is always room to discuss...
- they are weak to fire. You have a bow and fire arrows. You can take advantage of their weaknesses.
- you are complaining that you can't exploit?
- they do not come in 8+ groups. I have seen 3 tops and usually just 2 per pit. Did you find the mother of all pits, like 2 or 3 on top of each other?!
- 2 of them were not able to kill me, seeing as how I capped them and looted the pits. They certainly should not kill 2 maxed out players, apart from the first time you see them maybe.

I died to them the first time, sure. After that it was obvious that the slow prevents getting into melee range, and that the bow would be required.

I am not sure about any kind of nerf. They may need a balance pass, or not, but try ranged tactics to see if it helps you. The first time you run into anything is always a high risk, then you adapt until you have a way to handle it.