Problem with 2D animation extreme slowdown (Unity 5)

We have migrated over to Unity 5 and after removing all Component.convenienceRef and updating all shaders the build is back to a running state, however the editor update to 5.0 seems to have re-introduced an issue we were experiencing in 4.5 that was fixed in 4.6, that is that when the animationwindow is loaded with an animationclip containing ~20 animated transforms (including rotations) over 2 seconds @ 60 fps with only ~ 5 keyframes in the dope the animation process grinds to a halt. rotating a handle takes up to 1 second before firing the scene update where we are reliant on seeing this immediately in order to see the change in our character, this makes animating extremely tedious (prohibitively) and if you select a bunch of keys from the dope sheet and move them in the timeline to space an animation out you are in for a 5 second wait before unity will respond.

Thanks in advance!