I’m with Moriala one your first problem. Never had that happen with any of my characters.
For the 2nd one of pulling to many, that one I’ve done and I’ve learned I just need to wait til someone wanders away from the others to pick him off / pull him from the group.
I don’t know Berserkers, but if you’re using any AOE attacks that might be whats pulling in unrelated mobs.
My worst on that point was in SWTOR where the required companion had AOE attacks and in the first LARGE room, I had engaged the 1st mob (well away from the others), he did his AOE which covered THE ENTIRE ROOM! Suddenly it was me vs 50 npc’s!