That issue you describe though isn't a problem with sleet storm specifically, it's an issue endemic to all of Larian's effects - the game is ultimately two-dimensional, and all effects are two-dimensional. Sleep is a flat 2D circle, that will hit one goblin out of three if they are standing right next to each other on a set of steps, even if they all have 1 hit point, because it only effects the 'slice' that it's on, which is a 2d plane. The same is true of other AoE spells, and it's been an issue with Larian's game engine from before BG3.
Oh, really?! Perhaps I just noticed it with Sleet Storm because it has such a wide radius and lasts a while. Sounds like there are some issues with Larian’s engine handling 3D effects for spells but hopefully they’ll put the effort into fixing this for full release. It was a noticeable restriction on the utility of Sleet Storm and clearly isn’t great for other spells either.
