Thanks for the responses.
Our make up is
2 Assassin Tank
1 Sorc Dps
1 Sorc Healer
1 Operative Healer
We have tried many of the options suggested. Using predation, LoS even using the snipers sheid. Where it always seems that 1 or two people die.
I suppose its just trial and error untill we find something were comfortable with.
Assassins pop Shroud, Sorcerer healer uses Force Speed and pulls the Operative, Sniper pops Entrench at about 63-62%, Sorcerer DPS uses Force Speed and pulls the Merc.
This way the Marauder can be lazy and not use Predation which would make the whole thing trivial :P Though if it's not a Carnage Marauder, the Operative and the Mercenary will still take quite a lot of damage running out.