YESSSSSSSSSSSSSSSSSSSSSSSSSSS PLEASE.
I agree, adds more content for high ranked individuals and creates a challenge. If they're not capped I can guarantee only a few people will bother going through rank 3o dungeons as a rank 3o. They'll just get their rank 5o class or buddy to do it for them. The only other option is making it to where it's shut out to rank 3o and up which just cuts out a lot of possibilities.