A few items are shared with Shadow spec so they are not reforged or gemmed properly for Disc, in compensation of such I went just past the 2.1 raid buffed cast time threshold since I was already forced pretty close to it. Other trinkets available are Yu'lons Bite & Purified Bindings.
Basically my main question is regarding a Flex Tier helm I have. If I use it I will have 4 piece for Disc in exchange for giving up some item level and optimal stats. What I'm thinking is what is the best meta gem to toss in it. Should I use a Burning (Int + 3% Crit effect) or stick with a legendary (Int + no mana cost)?