I’m fairly new to, but I think if you do the three monolith quests, it seems like it resets the monolith modifiers.
I had the same problem with monoliths with a necromancer build that I found:
While the pets were awesome as promised, I kept getting one shotted everywhere. Maybe that build is for folks who know the fights really well.
So I restarted and did a sentinel build:
I’m level 83 plowing my way through level 90 monoliths like it was nothing and face tanking everything except big bosses like Lagon.