I don't know if I would go so far as to call it DOS3. DOS2 could get seriously insane with the ground effects! It's what made it fun, but still, insane! I don't feel BG3 is anywhere near those levels. However, I agree that it'll need to go on Cantrips because it makes them way to powerful!
Currently my best way to get through almost every encounter is having 2 mages with Ray of frost. You don't really have to do much damage as long as you make everything fall over. Next you just use you melee guys to kick their lights out while they're on the ground.
Of course there is the other stuff that's absolutely insane like the -2 AC when you accidentally stumble through an acid puddle! That's an insane debuff!
How much fire damage does that cantrip do anyway? I swear I've had Astarion die once because he got hit once, next got fire damage, and started his next round with fire damage. You could call that bad luck, but last time I checked the rules you'd get a save to avoid a fireball. Guess you're reflexes don't work against flames on the ground? (Which is odd because you can make saves against the Ice floor effect?)
So, my suggestion would be, keep the effects for real spells and allow guys to make saves against them. Remove them from the cantrips.
