The difference between Black Mage and Summoner is that Black Mage has a bursts phase astral fire and MP regen phase Umbra Ice which averages there DPS around the middles while the Summoner has a slow ramp up then they Bursts around their peak and after 4mins they bursts around their minimum. Their is no easy fix for the Summoner without breaking job balance. Since SE doesn't know how DoT DPS work they should rework the Summoner into a Pet Based Job. In order to balance a DoT DPS so players will use it in hardcore endgame it has to be balance around content and intentionally made overpowered otherwise it'll be useless.