Are there leaderboards available for ATT? If not, perhaps there would be significant interest from the community in creating them. This would likely be a web app as opposed to an ingame feature.

Nothing currently, but it's been mentioned in passing as something that would be a neat addition. Tagging as a Suggestion in the meantime.

The plan for this functionality on ATT's behalf has been postponed indefinitely for the time being with a reference to check out Data For Azeroth to fulfill this desire for now :)