I think the best way to experience castrum/prae is to have a patient level 60 friend unsync it with you. My friend and I turned on cutscenes and duoed it awhile back.. It was quite enjoyable. It's fun to experience it with the cutscenes, but this way, we weren't having to pull in others to wait with us. We were mobbing the entire floors (no skipping) for fun, so it should be possible to solo without too much trouble.