I think that if BW is going to make new advanced class for 50 - 55 the for Sorc i suggest.
Necromancer - For Male Sith Sorc Heal.
Nightsister - For Female Sith Sorc Heal.
I would personally think to add in a new ability for them would be Force Drain, in Which they train the energy from enemies and healing themselves and if force drain kills the enemy then it grants a bonus healing to you.
Well those are my ideas, i wonder what the dps would be because the advanced class for 50-55 would focus more on what skill tree you picked, whether it was dps, heal or tank.