Here is an anim I made when I was practicing for reaction.
http://i182.photobucket.com/albums/x141/Jit_13/test2.gif

Seriously dude, it was a horrible reaction...
Firstly, with the ground shakes, move the stickmen aswell. Not just the ground...
Secondly, if you were being beat up by some guy, would you keep your hands next to your head?
Well I know I woudn't...
Try working on easing a bit aswell....
Besides the above things (and a few other things) it wasn't bad if your pretty new to pivot....

Yeah, Blacky covered most of it.

It was choppy, don't move the stickfigure too much on the frames. Also, move every joint each frame, to get the stiffness away. Work on reactions some more, and smoothness the most.