I play the following: Sentinel, Sage, Commando, Gunslinger, Assassin, and Powertech. Soon, I'll be adding in the others I haven't gotten to yet, too. I've played them all a bit, but those are the ones I've done at least a fair amount of PvP on.
No offense to Snipers out there, but pre 1.4 I thought they were one of the most underpowered classes. Post 1.4, I think they're a bit better now. Not OP, but better.
Since Sages/Sorcs got nerfed in 1.2, I don't feel like anyone has really been OP (though I think Powertech/Vanguard is currently the closest, with Sent/Mara not far behind). Some are slightly better than others, some might appear better than others in certain cases, but with enough experience with all of them, the beauty of this game's balance really becomes apparent.
For everyone that is having issues with PvP, I would suggest trying out a different class with a different playstyle and see what you think. Most of them really are pretty different and cater to different strengths and weaknesses.
All this being said, until there are solo queues or some other balancing option, you'll continue to have issues where 4 or more players that are in Vent or Mumble or something together just faceroll people. That'll always happen when collaborators fight against soloists.
In conclusion, PvP in this game is pretty freakin' awesome. I like it, and I hope it continues to get better. Let's continue feeding them our ideas and supporting the good ones we like. The more we do that, the more both BioWare and the players benefit.
You are Spot on.