Yeah I'm not pulling on OK either. I have no need for mixed parties, and that seems to be the only thing his bssb is good for.
In other news, I did go ahead and kill nightmare necrophobe, I wanted that Affliction Break skill, which I now do have.
It's not just mixed. It's for all. Stacks with Shout and Sheepsong. Hell, nowadays, you can probably run this instead of Shout because of how easy it is to run up against the ATK softcap. Or you could do things like OK BSB + Atk Up + Crit instead of doubling up on the hastega.
That, and it allows OK to do very high DPS with it's burst commands (not like he can't do that already, with his access to ChainCharge) while doing silly stuff like Wrath + Entrust.