"Supercrits is on auto-crits, because ALL of the crit chance is applied to crit damage. They changed crit away from the surge stat, and rolled it together with crit chance. Now, crit chance increases crit damage, with crit chance over 100 percent contributing fully to crit damage. With assassins, you only really see this heavily come into play with a procced shock crit (darkness) with recklessness up, which does nearly double the damage of a regular crit. If you continue to build crit chance though, you will see the effect more and more during recklessness.