Sort of an early overview, Lianali (my sage) is currently level 16 and I haven't ventured into any flashpoints as a healer yet although I've done one or two group quests.
Healing: So far there are two main healing spells, a "bubble" and a cooldown that resets your stun and does a HoT to your entire party. And of course the usual resurrection spells.
Damage: In addition to lightsaber melee attacks you have two abilities to hurl projectiles at your enemy, two abilities to throw a wave or burst of force at your enemies (one knocks everyone in a circle around you away), two abilities that squish the mind and leave a DoT (an instant and a 3sec cast).
Then you get a bucket of utility abilities: a ranged stun, the ability to remove movement impairment, a force lift crowd control and a sprint.
So far the sage has been very fun to play although I'm currently feeling a little overwhelmed by choices. I feel like currently while soloing you have a lot of options for how to get things done. Whether that's jumping into the middle of things and hurling projectiles and swinging your lightsaber or standing back and keeping your companion healed while you use a few well places "spells" is really up to what you prefer.