The content was made with titan-egi tanking in mind. And bane only spreading dots to 3-4 nearby enemies, and a lot of other things that are different now. Yeah titan would lose aggro but but it was enough for him to hold targets you weren't actively ruining, or at least distract them during your setup period.

They really need to either lower the amount of enemies in some of them, lower the damage or add a warrior npc to tank for you like the SCH job quests has. Actually you do have a warrior to tank for some but he's not part of the fights usually