The goal of Disc is to pre-empt damage, and do as much DPS as possible. Go for ToF and Mindbender to maximize damage. Atonement spam, and use AA/SS to anticipate damage. The main thing to deal with is Chomp, as a mishandled debuff can quickly lead to things escalating out of control. Also, use Penance defensively to keep Grace on the tank if he's taking damage and/or before you SS.