We always leave at least 2 people on the boss. I then tend to switch between the boss and the add as necessary as I am normally the one watching for the transitions. We find it is a big help.
Also, not hitting the add until the tank has hold of it and it is in position helps as you have longer hitting the boss and you won't have to slow DPS if the add is on low health and nowhere near the edge of the platform to be pulled off. I hope that makes sense.
The little adds are easy once you get the swing of them. The worst bit is healers pulling agro on them. Just make sure your DPS are back on the platform when it spawns to maximise the DPS on them. They should die really quickly then. We also don't bother bringing the pillars down together, just kill them as quick as you can as the adds are really easy to control and kill once you get the routine going.