As said, Vigor buff happens after bursting.
But, Awakened Brahma has a +20 burst skill and a very lengthy guaranteed Combo skill. Both of which will be DEVASTATING after a burst. Even in the worst case scenario, Awakened Brahma will do 12 attacks worth of damage over her three Vigor turns. This does, of course, require her to be at full HP. That's almost two free turns that your team got (minus burst gain), and best case scenario is 18 attacks - which is three full turns!
In addition, if you have Raiko, it's somewhat likely that Brahma is back up at 100 burst with the Vigor buff still up. But having all that happen while Brahma is still at full HP is... quite unlikely.The encyclopedia in Sanahtlig's toolbox gives you a quick peek on all the upcoming SSRs. Next up is Dark Union Event, which gives two new FLBs, and a total of four for veterans.