And therein lies the problem. It seems that no one thinks to use their taunt ability as a tank in PvP to minimize damage, they just want to rush in like Rambo and be the hero.
Then it's a L2P as a team issue.
MDPS are GODS when backed up by tank and heals. Because 1) All the ennemy will try to focus down the guarded target, wich will then be focus healed by his teammates (in an ideal organized premade), and 2) Since the ennemy will have trouble taking their target out, they will start to run and scatter all over the place, giving your team an opening for a devastating attack on their backline.
SWTOR isn't much different from WAR as far as tanking mechanic works for PvP. These days, a guarded MDPS in WAR is the biggest threat, even though RDPS have the upperhand in PuG fights.