I mostly agree. However, there is one fight in particular where the long delay and long lasting nature of the gas cloud could be of use, and that is a certain fight in a certain warehouse with tight corridors and waves of enemies.
There may be places in the game where you would be able to chuck a grenade from stealth into a small room, then shut the door on a creature or lock it on human enemies so they are forced to stand around in the cloud. But I have yet to find such an encounter.
In general I don't feel they have as much utility as I hoped.