Just got back and it was hot and humid. Last year it wasn't so humid. Crowds weren't bad with the longest wait time was 20 minutes.
The best time to ride Rock and Roll Coaster and Tower of Terror is during the EMH time for MGM during Fantasmic. So many people go see the show that the park was empty. We made the mistake to see the Ariel show and there were about 50 people. Got out walked over to Tower of Terror and walked on. Left the Tower and Fantasmic was over. The crowd was huge. It took about 15 minutes to ride the Coaster and we went home.
If I did it again, I would ride the Tower and Coaster more often and then go see any shows once Fantasmic let out.