We were there last week and hit DHS 4 times. We never do rope drop, but the Tower lines were 10 minutes at the most during the last 2 hours of operation. I recall that the sign never dipped below 20 minutes but those things can't be trusted late in the evening.
By the time the first showing of Fantasmic started, you could walk directly into the library. One evening, we were too lazy to stroll over to R&R or Midway Mania and just stayed at Tower. It think we rode it 6 times in an hour.