Sorry but that is incorrect and misleading. I have a similar system to the OP, do professional video editing, use Word and Camtasia (just like him) and rarely see a spinning wait cursor.
The spinning wait cursor means the app has quit responding to system or user events. It does not indicate things are simply slow. When seen persistently and frequently it often indicates a deeper problem such as pending hardware failure, memory leak, etc:
http://en.wikipedia.org/wiki/Spinning_pinwheel
You should never really see a persistent spinning wait cursor on a properly written app. It should have a separate thread to handle those events and then post a progress bar or other UI indication of a long-running task. When you see recurring spinning wait cursors, that means something is abnormally disrupting smooth operation and the apps are malfunctioning, unable to service incoming events -- it doesn't mean things are just slow. It is definitely not caused by Fusion Drive.
I suggest the OP contact Apple support, report his symptoms and have them investigate. It could be a failing component or some disruptive app that runs on startup.