Update: just fought Omega. Didn't use Quick, so it wasn't as cheap, but still. I cast Thundaga on my dual-wielded Brave Blade and Ragnarok, which allowed me to do ~48,000 damage with Rapid Fire on the first attack. Omega responsed with two Mustard Bombs and Encircle, but I got one more Thundaga-Rapid Fire with a different character for ~12,000 to finish him. Two shots.