Before we go into quickened bending, I think we need to finish the discussion on the bending study feats while we still have ideas flowing. I agree with whoever says that circular attack is not the way to go for earthbenders with Waterbending Study. The best idea so far seems to be Pirate King's "Change Flow" ability, since it uses both the rootedness and defensive nature of earth (the bender stays in place and deflects an attack before it reaches him) and an aspect of water in the changing of the blast's flow. It's powerful, yes, but we can put some restrictions on it.

Waterbending Study
Prerequisites: 9 ranks in any Bending skill (or however many it was)
Benefit: The benefits of this feat depend on which bending skill(s) you fulfill the prerequisite ranks with.
Earthbending: Once per turn when you make a Deflect Bending attempt against an enemy bender's blast (this does not work against other ranged attacks), you may shape the wall of earth you create in order to change the flow of the opponent's blast, diverting the attack from yourself to an opponent instead. To do so, you must make a Reflex save opposed by half your opponent's attack roll for the blast. If you succeed, you may angle the blast to hit any opponent within a cone extending from your opponent to yourself and ten feet beyond you. The opponent must make a Reflex save half damage (against your save DC) or take damage according to the original blast damage.

A bit complicated, I must admit. Thoughts?