This is what I have observed from my perspective of things.
I think the key classes to make this work are:
3 PLD/NIN + 1 BRD + Minimum of 3 Healer/paralyna fiends + everyone else on DD.
I think with these keys in place we can consistently do byakko with as little as 12 people (with some practice). I know alot of you think Byakko is this 20-30-40 person thing but screw that. I could personally give 2 shits if another linkshell knocked kitty over in 2 minutes. It doesn't make the gear that drops any better. Its the same whether it takes 2 minutes or 10 or 20. Quality of TWOI means we can do more with less and if it is harder or takes longer so be it.
There are 4 main destructive factors about Byakko:
Fast attack speed with triple attack
Enhanced movement speed (this one is the only one that is pretty much unavoidable)
Shitty Paralyze
Insane Evasion
Bard:
The bard attacks two of these areas. First it slows down attack speed which helps to /nin tank the kitty. With elemental seal + elegy you can lock in like 7 minutes (from what I hear) of slower attack speed. The bard also greatly enhaces accuracy with songs for DD party. Also I feel like 2 tanks probably can handle kitty if there is a bard but I like the backup approach so 3 gives me a comfort level.
PLD/NIN:
This last go about with byakko I would say without a bard a solo PLD/NIN has a lifetime of about 3.5 - 4 minutes. A third pld/nin could help to extend that time out longer. This solo survivability factor could increase with a bard but I think in general rotating 3 pld is where its at.
BLM:
Worthless.
DD:
Think we are fine on this front, just would have faster dmg output with ACC+ songs. Byakko is doesn't take a ton of damage from WS etc.. but it doesn't feel like he has a ton of hp either. I think the key is making every swing connect.
HEALER:
I think we are good on this front too. Keeping paralyze off tanks and curing up hasn't been so much of as long as the pld/nins have the cat. No amount of MP in the world can correct the kitty rampaging though DD though. So I think if we can keep kitty on pld/nins we are strong in this front.
If you have any strategy comments please post replies.
TWOI!!