Sounds like you'd still waste a lot of time logging in to a character where the boss had just been killed by the other four thousand people camped there waiting, and you'd still have to wait because you just missed the boss.Park 2-3 characters in different public dungeons, put them right at the boss. Log in and out killing bosses that are up.
This is my solution - haven't had any issues in my location with overcrowding and 15-20 an hour is acceptable to me. I can't tell you where it is but I can fish in between bosses.3 Minute Timer is in place for Skull Drops.
So, you can't get them any faster than that.
Find a quiet public dungeon and make the rounds of the bosses, making sure you keep 3 minutes between kills.