As far as i am aware, there is not ging to be a review of dla, so i dont know what you syaing about that! the review is going to be of incapacity benefit, which you say you do not get. i would imagine that that is because of not having enough ni contributions?
personally, i dont know whether saying blanketly that people with depression could work is right either, as it can be just as debilitating as a physical illness. I think everyone should be reviewed individually as to their capacity to work, and that is the only way of weeding out the "swinging the lead" people as you call them. Again, i think benefits shouls be reviewed on a regular basis, and increased where nessacary and decreased where nessacary.