Rigging Set-up Revised

I began animating the attack and realised immediately that there was something wrong in the way the inverse kinematics were solving their movement from point A to B with rotation including for the staff. To elaborate; when I animated the swing of the staff for the attack, the frames between the first and second keys caused the arms to move erratically and stray away from actually holding the staff (they would just fly off and come back at the last frame). I spent quite some time trying to figure out why this was happening, after trying things such as removing the right hand's constraints and trying to animate it to follow the staff, which produced poor results, I finally figured out how to correct my issue. The problem was, I eventually found, was that the way I altered the rig so that the hands moved with the staff was incorrect, or rather not done to fine detail; I had made the groups which controlled the hand movements in a way so that their hierarchy didn't control the rotation the way I wanted, and that the pivot points of the actual groupings were incorrectly placed. It is something that has wasted a fair amount of my time, but also something that I have learnt from the hard way and will make sure to never do again. 

Here is what was happening:

The first two images are the start and end of the key frame points, A and B. The rest of the frames are how the rig modifications I added for the staff I spoke about created movement between point A and B. The solving of the inverse kinematics using that set up were terrible.

Here is the latest revision of the rig, which I have tested multiple times with different parameters to make sure it will work, and everything seems to be working to what I had expected the first rig to accomplish:

Here you can see the hierarchy of my new rig set-up. I used a locator to place where I wanted my group's pivot points to be and then created the groups, placed the hand controllers into the group and then snapped their pivot to the locator. I then created a curve controller using the EP Curve Tool and traced around a polygon square, then deleted the polygon square so only the curve remained. I snapped the new curve controller to the locator position, then deleted the locator so that all the pivots of the hands, staff, group and curve controller were in the exact same place as where the locator was.

Here you can see the final result, I have the newly made Staff_Controller at the top of the hierarchy.

Now the issues you saw before, with the erratic movement between frame A and B are no longer there, and it moves as intended between frames.