Actually, Queens and Druids aren't really necessary in a FG rainbow. They help in the endgame, but that's about it. They are almost never crucial to victory. Since so many rainbows use quint, it would be easier to use lava golems. The damage growth is less compared to a Queen, but it's half the cost for the ability, and fire/earth aren't used that much anyway (RoF's, PA's, and Pulverizers). You could leave the Druids in since you can usually get a good enough mutant out pretty quickly, and they really don't use up much life. And a lot of rainbows don't use bonds anymore. Since FG rainbows are driven by stalling and card drawing, taking more defense couldn't hurt.
Fire Golems die first turn even if quinted against Fire bucklers. Lava Golems are very, very vulnerable, a ffq has 7 hp starting out. Mutants are always a big help and can help when you know your opponents have miracles (you can up a firefly to a golden dragon with 13 attack to kill them the turn before they miracle.
Off the top of my head, I can only think of one FG that uses fire buckler. Besides, you can usually get rid of it unless you're unlucky (I've only played one game where he used PA on his shield the same turn he played it). Octane may use fire shields though, but I've only fought him once, so I wouldn't know. Still though, that's what, 2/18 FG's that use fire shield? Plus, for fire shield to kill it you have to play it while the shield is up. If you play it before the shield is played, growth keeps it from dying. If he plays the shield first, destroy it. If he PA's it, you're usually screwed regardless. Skeletons/fireflies only last for two rounds, druids for three, oty's stop growing at best, and FFQ's can only put out two fireflies at a time. Lava golems are one of the few creatures that will never die from fire buckler, unless you run out of quanta or play it after a fire buckler is played.