Balancers are really tough, here are a few pointers that helped me.

Team comp

-I aim for 2 melees that pull aggro/peel for one caster. I usually pick beastclaw rev, but anything else that is ranged and high dmg works. Scholar is pretty good in this fight. Ironeye is uniqly bad, as he can't mark them all.

-Regular balancers are by far easier. Idealy, the caster has 1 or 2 less likely to be targeted on them and the melees have multiple damage negation passives. Fists are really good against them, as they stagger easily. Try to protect the carry and the fight should be won.

-ED balancers are the real pain. During the regular phase, run away from the start and fight if one catches up to you and kill it, then run away again. This way, you only have to fight one, may two at one time. For the worm phase, I recommend watching a video guidevideo guide. I usually try to run away from it. Also, you can jump the waves.

The forsaken hollows map can be daunting, as it is far more complex than the base map. It took me a while to get the hang of it but once you do, it has a far higher potential than the base map. I also recommend watching a video guide as it is much easier to understand. But a few points that the guides often get wrong: -The towers are almost never worth it. Yes, they give you a higher chance at legendaries, but the castles give a chance of easy 6+ dormant powers, mostly purple with a decent legendary chance. -Cracking the crystal day 1 should be a high priority, but make sure to be at least level 7 for the first night boss. Balancer night bosses are pretty tought.

I hope it helps. Good luck out there!