One of the reasons why bio isn't that great of a launcher is that you don't have to (and shouldn't) JA every PA you fire off from a launcher, due to how slow the normal attack is. A non JA'd Cluster/Cosmos/Divine will generally do enough damage to one shot SH trash mobs (First Hit helps) and if not, Bio Spat's potential certainly isn't helping you get there.

I haven't used Flame Bullet in so long that I forgot how it works, so I can't really help you there.