I have a report that returns information close to what you're looking for. Try joining these:

Context is optional, if you don't need it for your reporting, you can leave it out. (I like having that info).
WF Voting Event Audit contains the user's vote and user comment. It is only filled in if the task is completed. If you want to have this info, but also want to return open tasks that aren't completed yet, you'll need to use the "Outer Join Against " option on the join, set to WF Voting Event Audit.
WF Assigned Activity is where you can get Task actual start and actual finish
Workflow Process is where you can get info on the overall process, like start time and finish time as not all tasks may be assigned when the workflow is initiated.