well white ichigo doesnt he buff assaulter damage by like 25%? or was it 15.. not sure.. but either way holy shit LOL
edit: shud've read the previous comments my bad!
It has actually a good example, cuz 12% orihime buff would not do 2x damage difference even if it stacked. Not to mention Curls and his w.ichigo I would guess these buff stacks work in a wierd way: lets say normal stack should work that way 100 x 1.1 + 1.2 = 132%, but it might work like that instad: 100 x 1.1 x 1.2 x 1.1 x 1.2 x 1.1.... - in other words every buff stack while previous buff does not go away.
Would be good if somebody with a buff partner could test dat on protect seireitei event today. Ps: also when i fight these people in arena/csb/hma i do not nocite any huge damage difference, it seem it work only in pve.