Do you have a legend dived Ramza with shout? I used the support nightmare not too long ago to powerlevel a soulbreak I got for Irvine, and it can be cheesed with Cloud USB.
Assuming you have a dived Ramza, give him your best dps gear and a +40% or 30% damage RM. Entrust Ramza on turn one, use shout, kill the first wave of orbs. When p2 begins, have some other units disable the beams, have Ramza call in a cloud usb RW on the main boss, then have Ramza use some hard hitting support skills to dps the big orb (affliction break hits the hardest if you've crafted it, else I think fullbreak is best). You want to stick to support skills to dps with Ramza, since his legend dive gives a bunch of +damage to support attacks.
With the cloud RW, you should be able to take out the big orb before the physical beams respawn and win the fight.
I haven't done the tonberry fight in forever, but I remember that one sucked when I did it.