well my setup is at the moment 2 - navy BS's and 1 logistics running lvl4s.
The 2 BS are equally equipped armor tanks, they both have T2 medium drones (hammerheads in my case).
The BS that pulls the most aggro i put my drones to guard/FF. (means they attack everything attacking the BS)
This also includes my logistics that has T2 light drones.
The way drones work most of the time when put on guard/aggressive is, the light drones goes after the friggs as primary and the medium take on the cruiser size ships as primary.
So the drones are more or less keeping busy the whole fight with out micromanagement.

The thing is, in some missions you have multiple spawns. they will not always target the Toon nearest to them.
I had that setup before with 1 tank 1 all out dps and my logistics. It got complicated to keep track who had what aggro, and constantly jumping ships in and out is lowering your dps.
So i found that 2 identical tanks + support was better at least for me. Faster to make ISK/H.
This setup works good for me at least, I make about 80 - 150 mil a day with out playing more then 4h on average.

Ehh btw RobinGB, with mission group you mean pve missions or mission group for pvp?

I use to be a pirate, but i have not killed anyone in a long time and i have never used more then 1 account when pvping.. :|