I would normally expect an assessment to take 1 to 1 1/2 hours, we do sometimes hear of them going to 2 hours but I am not certain I have heard of one lasting as long as yours.
I do think you should make a complaint but you don't want to make one complaint and then find that you are unhappy with the report, I'm hoping that this won't be the case and have to make a second complaint.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems