So now with shield oath, I am still losing aggro to level-synced ARCs or BLMs, but seems to happen less often, and I seem to be able to get them back more easily with provoke.

In any case, I never had this happen before in any dungeon, but in stone vigil, I find that the bosses are fairly straightforward to tank, and actually never wiped once to them. But the mobs were out of control. It take only a Aevis or some other dragon to two jump into the mix and it is a wipe. And I make sure not to tank where that flying dragon flys in fries people. I thought the bosses are supposed to be tougher to clear.