This looks like it would be one of those decks that could work decently against some FG's, but it would be destroyed by others. Sometimes, very fast rushes are too much for a single Oty. Ferox, Fire Queen, and Chaos Lord (sometimes) come to mind. You would also easily deck out against FG's with Miracle, especially if you get your Lava Destroyers late. Puppychow's suggestion would remedy both of these problems. You could also try to fit in a Permafrost Shield, which would at least use up some the unused Water quantum.
Another suggestion could be to take out the Steals. Some of the current anti-FG rainbow decks work just fine without them.
So, possible changes:
-2 Steals
-1 Octopus
-1 Quint
+1 Permafrost
+1 Pulvy
+1 Rain of Fire
+1 Eternity
Permafrost helps against Elidnis, Divine Glory, Scorpio, and Gemini. Pulvy works wonders against Octane and FG's that use Hourglasses or decent shields. Rain of Fire and Eternity are pretty much self-explanatory.