Shield oath is nothing but a weaker inner beast, even without a nin in a group you shouldn't lose aggro to anyone unless you have a monk.

Monk is the only class that cannot decrease enemity, and if your blm doesn't want to spend time getting quelling then he doesn't need to be raiding, point blank period.

Even in a pld/drk situation, most of the dos is going to come from your group, it only means that BOTH tanks can sit in off tank stance without a issue. As a pld you should MT because your combos generate more aggro naturally and the drk does not.

You don't need a nin or slashing to clear this content you just need to work as a group.