With regards to how much boat traffic there is in the Backside, There is rarely as many as 4 boats per morning diving the Backside, because why would they want to fight over 6th, 7th and 8th? The race is to get the Reef's End mooring!
The Captains drop groups close to the wall and then follow the bubbles from a couple hundred feet off the Wall. Departures from Kihei Boat ramp are NOT all at the same time, so starts and ends of dives are also NOT at the same time. Depending on the operator, divers/teams will be sent up as gas dictates; hoovers do not end the dive for everybody if you dive with a responsible operator.
Slight overreaction on my previous post as the "big waves and ripping current" statement was directed at Molokai. Diving Molokai on a set schedule is how you end up with injuries; responsible operators dive Molokai when conditions AND guest experience are proper for those dives.