Why am I always losing aggro on Ultima Weapon?

[Llevron]

Hey Tanks,

I notice that lately I am always losing aggro/hate on Ultima weapon and it goes directly to a healer. Fortunately I always carry provoke on my back bar, but im trying to figure out what it is im doing wrong. I have sat back and watched other Tanks do it and a few of them have had the same problem, a few dont. So it must be something im doing wrong, correct? I start this fight off like I do any other, Long range aggro -> Spam overpower a few times and go. But for this guy its not working.

Honestly for this instance it really doesn't matter as we burn him down enough anyway. But I dont want it to be a mechanic I dont understand that bites me in the behind farther down the line.

Thanks for the help!
~Young Glow