I’ve personally found great effectiveness using cloud of daggers maybe more than any other spell. Funnelling enemies through a passageway with multiple cloud of daggers cast on the spot is probably my current meta. Then I utilize thunder wave/ black hole to keep the enemies on the other side of the daggers once they make it through.
Another thing if found amazing success with is getting a party to strength 20 as fast as I can, which then I find 90% of enemies can be thrown off cliffs for instant kills. Throwing enemies off cliffs also only requires stealth checks where the body hits the ground and dies.
Lastly there is a fun little cheese strategy I’ve picked up that I don’t see anyone talking about. If you cancel an improvised weapon attack with an NPC before you deal damage, you can move NPC’s without angering anyone.
I refuse to throw someone off a cliff, they have things to sell!
I have 2 patterns, that sort of overlap, depending how the fight is going. I have my paladin and Karlach up front. I have shadowheart just a little back usually next to my “option” character (4th slot rotates out a lot based on needs, but usually Frost mage Gale)
Example, use someone to cause a giant ice slick on the enemy, right in front of my front liners. Then use shadowheart to possibly throw an Insect Plague on top. They have a heck of a time getting to me, and if they do they get to meet a paladin who’s really hard to hit (decent AC + light cleric shadowheart) and Karlach with aspect of wolf means there’s a beatdown right there. This pattern works really well for the most part, there’s always exceptions.