Mike,

Dipsy divers are still used... even by a lot of charters, they just use them a bit different than what you would as a primary trolling weight.
The reason that most of us do not use them exclusively is because you can only really run about 6 rods max. and that is if you are really good and know what you are doing. 2 out each side and 2 straight out the back.

With big boards you can run 8-10 rods out each side. A lot of charters will run a dipsy straight down off the side. Dipsy's dive straight down enough to run them along side the boat and still reel in the other rods. Many times I run a Dipsy or two right on the bottom and forget about it all day and see if it picks anything up.

Bandits to not require any additional diver or weight to be able to place it wherever you want in the water column.

-Matt