The obvious one is, Crit damage provides bigger numbers and burst, but the more intricate thing is how it affects rotations. Both Assassination and Subtlety rely on a certain amount of Crits to generate Combo Points. Hopefully we’ll have secondary stats on a more equal footing, where we won’t think of a particular stat as trash to reforge away from, and at the same time, one stat won’t be so much more better than the others, that we feel forced to stack it without restrictions.