When questions are asked but deemed off-topic by the community and subsequently closed, should there be a requirement for reasoning and constructive feedback before voting to close?
I don't think this is necessary. In the majority of cases, the closure message and the FAQ linked to in that message do an adequate job of explaining the motivation behind the closure. Now if only people would actually read it. But that's another matter altogether.
That said, especially with newer users or other special cases, I do sometimes leave a comment explaining my motivation behind a vote to close. Perhaps not so often for off-topic though. More often for "not a real question", since that one seems to lead to quite a lot of confusion. (Hey, this thing has a question mark at the end. How is it not a real question?).
Should you as the OP be terribly confused about the reason, then by all means take it to Meta. If you constructively ask for the motivation behind the closure, you will more than likely get an in-depth explanation. If you're still in the hot steaming "What The F" mood, you might want to give it some time, since rants are not often responded to in a positive way. But if you're simply curious, please do ask.