I was under the impression all classes would be able to fill all roles, rather than being restricted to DPS / tanking / healing. Am I mistaken?
Recently, on the official forums of the game, it has been confirmed that 3 of the 4 base classes on either side (Republic and Sith Empire) will have an advanced class that can spec to be a fully valiable healer. Previously, it was asumed that it would only be the 4 Advanced Classes we already knew of; the Jedi Counsular Sage (formaly known as Wizard), the Sith Inquisitor Sorcerer, the Smuggler Scoundrel and the Imperial Agent Operative.
Though it's now 3 per side, the third class on each side to have a healer spec is not yet known. Most believe it will the Bounty Hunter Mercenary and the Trooper Commando, to keep the trent of ranged healers and because the Mercenary and Commando Advanced Classes use medium armor, unlike the heavy armor Bounty Hunter Powertech and Trooper Vanguard.