Why should a group be forced to take certain classes?
We tried to do this with two melee and a Jug tank and couldn't get any better than 50% on the first boss. The fight has way too much going on for a melee group to be able to complete it on HM. We wiped for hours and ended up going into the red for durability twice before just giving up.
(Everyone was in almost full Rakata)
Then you don't deserve that Rakata!!!
Melee just has to stay behind the boss...which should be the case in nearly every fight. If your heals have a dispel then you can just get rid of the dot. It was only a problem when our dps made a mistake and got to close to the tank.
Healing kept be busy but nothing does a TON of damage other then incinerate. Its just when someone is getting zapped, while in a emp field, standing in fire with adds on them. Then the health starts jumpin down.
DPS has to be aware and avoid damage from as many sources as they can.