no they're not, the normal attendance at the arena is below 14k (I've worked there for 4 years) and an hour and a half before support isn't an unusual doors time
I was told by a friend who worked there that the capacity of an end stage floor standing event is approx 19k. I'm sure the normal attendance is indeed less. Even so I've been to many with door times of 1-1.5 hours before, though the majority do seem to be 1.5 hours now, so I guess the 2 hours of Metallica is justified, it just seemed like a loooong time!