Gas cloud coverage broken on stairs

Hello!

I use Gas Grenade skill with huge increase to the area of effect. And I catch, that some maps have problems with that.
In particular, it have a problem with stairs and climbs - if there are any difference in height.

Cloud visually cover the place but does not affect monsters. The same way as obstacles and closed doors. But in this case nothing should block the gas but climbing.

It looks like the gas cloud is 2D circle, not the sphere or cylinder so it does not collide because of different level.

It makes this place are pretty nasty for my build, as cloud does not affect them, but they shoot me at free will.

For example Grim Haven (Ezomyte city)
https://imgur.com/a/tsMObmH