I agree with Express being an issue. RIP also huge--had two 20-person tours cut in front of me in maybe a 5-minute span; an extra 300/hour would test even a people-eater like Haunted Mansion on a busy night. Also, to be blunt, abuse and fraud with GAC is probably even more rampant than it was at WDW when the Mouse changed policies.
I agree Express the only way to go. Even with express, 20 - 30 minute lines standard for the popular houses.
I think it's fair to say at this point, the system is broken. 9 houses and Diagon (which seems popular) and it doesn't make a dent.