I like u82 and the new mastery feats. Great job SSG
Note how spells with two elements like "Icy Flowers" or three elements like "Prismatic Strike" will potentially benefit 2x or 3x from the mastery feat boosting opportunity. I estimate adding one mastery feat to my build will add about 12% total dps output, ergo optimizing a build around a rotation of spells that all have 2 or more elements matched to a mastery feat may increase total dps with each tier i.e. each additional element
2 element spell = +24% total damage output
3 element spell = +36% total damage output
Perhaps there's a way to leverage this new feature ...