This is excellent! However, can I suggest adding a single frame before the big swoosh? At the moment, there's just a hint of entry into the motion missing. It's like he winds up, then magic-flash-and-boom-done.
I realize that a single big swoosh frame can make for a nice effect, but when working on such a level of detail like you are, it pays off to at least hint at the full motion, like you're already doing with plentiful follow-through.
EDIT, to continue being an asshole: I hope the way the flash arc disappears is just WIP. This sort of lateral fade-out works great for tiny SNES sprites, but on your scale this cries for a great fire/steam/ripple/sparkle/confetti effect.
And this is nothing comparable, but I wanted to throw it out there anyway...
