Yes, I clearly get the fact that when you shoot at 1.8, 2.8 versus a 5.6 or 8 you are going to get a much shallower depth of field. If that's what you're going for, the DX has an advantage as the DX sensor has an even shalloer DOF than the FX sensor.
By what measure does DX have a thinner DoF than FX?
However, sometimes you don't always want that razor thin DOF. On his D7000, if he's at 85mm focal length, 8 feet away from his subjetc at F2.8, he is going to have a in focus range of less than half a foot. Most people's heads are more than that so he'll either need to step back significantly - thus changing the composition - or shoot at a higher aperature which - negates the effect of the F2.8 lens.
Look closely at most portraits. 1/2 a foot DoF is a lot! Many many portraits have a much shallower DoF than that, often to the point of the nose being softer than the eye.