I`ve been doing quite well leveling as a healer - damage is nice, has great soloing capabilities (able to solo 2+ quests easily with khemy :-) and it makes it a lot easier to find groups for flashpoints). Now toyour question, you'll need a dedcated healing spec after a certain level because as mentioned before you'll have issues with force management if you dont. On a sidenote, to those who believe leveling as a healer is a lot slower, that's wrong: might not be as fast but nothing too significant that should make you alienate this spec in the first place (tip: keep your companions equipped).