While having access to a blacklist is very handy, I do wish this could be expanded to include people from other worlds.

As the main problem I have found is Duty Finder Trolls. They will sign up for a run and intentionally mess up runs or AFK for the entire run forcing others to leave. While if this is what they want to do its there choice and they can do what they like, but I personally would never like to see them in a duty finder again.

Even though the odds of getting the same person in the Duty Finder can be quite low I have had instances of the same person show up multiple times and mess up runs / boss fights.