Stuns usually cause the mobs to scatter somewhat. This is why a lot of times an AoE immobilize is required. On the other hand, an AoE confuse like Seeds acts like a pseudo taunt since all of the mobs will gather to attack one another (especially with melee mobs). This synergizes with AoE attacks and other effects like Drain Psyche which prefers enemies to be closely spaced. As a result, I would say that Seeds of Confusion is the best AoE mez in the game.