Dragons has an insane capacity, something along the lines of 3,000-3,500pph I believe. That means for any kind of wait to form, more than about 3,500 people have to enter the ride in the course of an hour. In reality, a 10 minute wait is at most a 2 or three train wait because it takes about 5 to walk through the line to the station anyway. And even if you account for operational inefficiencies like down time and groups of two or three inefficiently using rows leaving empty seats and take capacity down by 1/3, that's still about 2,000pph. A 9 hour day (seems the park is usually only open 9-9 during the busiest of times, so 9 hours seems a good compromise) would see 18,000 riders at the reduced capacity, or more than 25% of an extremely crowded day at the park. Taking into account that the entrance is almost invisible in the Wizarding World (Seriously, what were they thinking? I almost missed it the first time the area opened completely, and I knew what to look for!), and a lot of Potter fans aren't as likely to want to ride them, that is pretty darn good. I expect their daily numbers are probably somewhat close to 15k (I recall when I was doing nightly rider counts at Cedar Point, seeing the sheet and Raptor and Magnum constantly having between about 12-14k), so that is really quite a good ridership number.