A 5megabyte patch shouldn't require 4GB of free harddrive space.
This cannot be steam's fault because let's say DOTA2 a game steam makes themselves can manage to patch itself without demanding it's entire installation size be available.
Please come up with a long term solution to this problem. as path of exile is a competitive game which features loading screens owners of older smallish SSD's really cannot afford to have this be the way patches work. A solution must exist, please implement it.
Path of Exile requires TWICE it's actual harddrive space to reside on my SSD. I don't have room for that. So I don't really play much anymore if ever.