Again, 2 minutes for an entire White Tyrant run, 4 with only 2 people.
EXP and AP, what you're talking about, yes, Hidden is the most efficient.
Once you've hit level 44, EXP stops mattering, and White Tyrant is the fastest mission for pure AP.
Fastest Hidden run I ended with 57:26 on the timer. It could probably be even faster with 6 Spear Lanns.