When he uses Howl, run behind him and WS.
Not enough emphasis is being put on this. Jobs, buffs, and setups are not nearly as important as understanding the Howl mechanic.
He continually builds up Damage resistance. The only way to reset it is for the person with hate, to tank from the front and force him to use 'Howl' this will lower his damage resistance, but also increase his damage dealt to you, so managing this is the key to the entire fight. If you stand in front the whole fight, he'll howl non stop, and deal too much damage for you to survive. If you don't force any howls, his damage mitigation will grow too high and you can't deal enough damage to him.
Also, DD's need a LOT of accuracy, in the 1400 range to cap. So either need buffs, or DDs who can naturally hit that with sushi. Lastly, try to get DD's who don't sit in full DD gear while they're stunned for 30 seconds eating full power Meteors like morons, or don't know what hybrid/DT sets are, but good luck with that.
Barthundra from a Whm with 500 Enhancing + Ebers set + merits is nice, but I did it on my gimp *** Whm multiple times without a problem. Just stand with the DD's and spam Curaga3 > 4 back and forth for each AoE. If they die before you get unstunned, it's because they didn't swap to DT gear.