I just watched the tank spot video on this and I get the feeling it's a bit old-ish. John and I have had some practice on this fight on 25m and we did see a positioning that guilds are using very successfully.
basically they tank the big boss where he lands, nose to big bell. all the melee stand on the left foot, all the ranged just behind them on the left near the gong. When the sound waves come out, all the melee move to the right foot and all the ranged move to the right rear, near the right gong. On the next wave, everyone moves to the left, etc. When tracking is on someone that person moves to the closest wall, right of the raid if they're right, left if they're left, and runs to the tank, meanwhile, the raid moves to the other side to avoid tracking as well. It's like left right left right, same as video, but in a different place. This place is easier for gong people, because they know exactly where sound will be, easier on tank because there will be no fire under him, etc.
Anyway! That's my suggestion!