probably harders boss ouside of last one with HM. Typical for DLC dungeons when midlevel bosses are way harder than last one.
So the question is: that stranglers who prevent green spiders to hit Maarselok (or whatever they trying to do) sometimes just overwhelming the group. What we must do to avoid it ? Even in first wave, sometimes they spawn like 2-3, sometimes they spawn like 5-6 almost instantly.