CM Mastery. Vivi's BSB is 100% the way to go if you're still using the Hope BSB strat or other options.
Melti was at 50% before it even got a turn off, and of course the next 2 attacks were scripted, so I didn't even see a Bioga until it was at 10%. Thankfully when I did Kuja was topped off and had already queued up his burst command.
Never used Meltdown or Eiko's shared medica.
Kuja was hitting 2.5/hit on BSB entry and 9.2/hit for each command. That's with Mental BD up and no FB.
Spoiler: show
Search the friend code tracker for Vivi BSB's that havnt been all friended out yet.
https://friends-ffrk.rhcloud.com