I'm not sure what you are using for a game engine here, but I have seen a method in Unity where you draw the basic sprites and then animate them in the editor using bone/rigging techniques similar to 3D animation methods. I'm not sure if this reduces the work load as I'm pretty new to game dev. in general, but this came to mind and I don't think anyone above mentioned it.
For an example of what I'm talking about see - http://gamedevelopment.tutsplus.com/tutorials/bone-based-unity-2d-animation-introduction--cms-21364
This maybe is available for other engines as well? Either way, best of luck with your project!
*edit* Here is maybe a better example - http://forum.unity3d.com/threads/2d-puppet-rigging-tips-tricks.245564/ *edit*