Affliction tolerance is nearly useless, most of Mordred's debuffs are DoTs (which are only slightly better than useless for a maxed team), and the remaining DoTs rarely land. So really, what people use Mordred for is Affliction resistance down and Black Propaganda. That is a potent combination, but more heals adds up over the course of a long fight. We still haven't seen the Accessory quests yet, which seem like they'll favor endurance builds. Damage builds work well when the boss has a rage meter or low HP, but they're less effective when high damage doesn't avoid the punishing attacks.