well, it's a matter of preference, bracket, comp, etc.
You need a lot more resilience as a disc priest then you do as a rogue. This is simply because rogues had a lot of utility between Cloak of Shadows, Vanish, Shadowstep, Sprint, Evasion, and that other one I'm forgetting that lowered physical damage. In most cases, rogues were better off stacking pve gear/stats to maximize damage output, since most people ignored them completely.