Unfortunately it is through companions, their abilities and their acquisition rate where we clearly see that Bioware did not originally intend this game to be a MMO. It has all the hallmarks of a single player game. In a MMO companions would have similar traits for mirrored classes and acquisition would be at a similar rate. The Republic seems to get more companions early on, Jedi Knights the fastest for their true second companion.
I voted BH simply because its a full blow healer that really works.