Sorcs/Sages are fun if you play a specific way. As others have mentioned, they have amazing utility in pvp and have lots of cool abilities. For those that typically complain about sorcs/sages being useless, they are probably using the middle skill tree where most of their abilities are casts.
I have a Balance Sage (not sure of the name-equivalent for Sorcs) and I'm pretty geared. I have no problem taking out a mara/sent or a jugg/guard. You just need to learn how to kite, use LOS, etc. Know your limitations, don't go running head-first against a gap-closer and expect to win. Kite him, root him, interrupt, stun, etc. Unless the "gap-closers" are fully geared, I typically have no problem burning them down 1v1.
You can also do great CC. I'm going to use the Sage terms, but I'm sure you'll get the idea. In a Civil War match, as a Balance Sage, I went grass with 1 other person. I was the one to intercept. I used speed burst right away and used Force in Balance (an AOE) and immediately slowed ppl by bringing them into combat. I used "Force Slow" to slow down one, "force stun" to stun another, used my INSTANT "force lift" on the guy that broke his CC breaker, and then then used my knock-back. Basically, I used all my abilities to slow down 4 players that rushed grass, and my teammate that went to get grass capped with no problem. In huttball, i like to use the instant CC as someone crosses the firepit, or rush to the endzone and pull ppl up from the pit or down from the catwalk. In voidstar I pull anybody in danger to the side and bubble them and drop a couple quick heals. I can go on, but I think you get the idea. Just learn your abilities and your limitations and you will have a blast using Sorcs/Sages
Plus if you know how to DoT people properly, you can easily hit anywhere between 400-600k in DPS in a full match.
For healing, I think this is fun especially if you have team mates guarding or kiting for you. I think its fun but of course you always get targeted right away.
For that middle tree... I cant think of the name but for Sages it's Telekenetics. Most of those abilities are casts. Easily interrupted. As fun as this one is, IMO it's the worst in pvp.