Holy Shit. 6 Full Hours, you must be close to killing yourselves ./joke
I remember wiping on Nefarian in BWL for 3 full weeks monday - Friday night from 19.00 - 00.00
in the off hours we had to go farm for Fire protection Potions for the next night.
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In your actual situation whenever it seems like you hit the same wall every time, I would take a 30 minute break for people to think stuff over.
Then come back with fresh energy and keep going.
Remember Bosses like that is not supposed to be something you kill in 6 hours.