I had posted previously about my troubles with this fight. pre patch 4 it was challenging (I party wiped at least once each time) but it wasn't frustrating, just challenging and, frankly, fun (I don't mind dying every now and again). But now I party wipe immediately and keep doing so - I haven't even come close. So I avoid the fight altogether for now. Yes; there will be those who are "I don't have trouble, you just need to learn to play the game" (massive eye roll here), or even exploit a glitch or something not a part of actual play as their work around. The point is that this fight is far too difficult now with level 4 characters v. Level 5. I am hoping for it to be more balanced. Larian seems to have a little trouble with that concept.
It's always the same... The game isn't balanced at all because their mechanics unbalanced everything.
Wants a few tips for this fight ?
Focus on shoving / thunderwave.
Use the speed potions if necessary and if you're starting the battle : void buld + cleave or even better : the buggy moonbeam (buggy or OP, I don't really know if it's intended or not or if this is another "engine issue")
Don't forget to use the OP GWM feats. With the free advantages due to backstab you'll deal massive damages, eventually to 2 targets on the same turn...
And don't forget to equip 2 strenght weapons to any character and drink a potion of giant hill strenght + coat them with poison to deal massive damages.
And give a shied to your characters before you click "end turn".
Hide as a bonus action if necessary so they won't try to find you.
And of course as usual, don't forget to dip you weapons for additionnal damages if necessary, stay higher than them and backstab them with your melee characters...
This encounter is very hard... or easy... Like most encounters in the game.
I did it in my last playthrough with a single druid.
Use the easy win buttons and mechanics or get frustrated. This is how the game is "balanced".
(of course depending your tolerance to frustration, you'll use more or less "win buttons/mechanics")