IMO, some classes just scale better than other classes, especially when you hit level 50. Sages are very competitive until level 50 and then they are pretty much forced to go heals in order to contribute as much as another class would in their place.
I agree with the previous comment that Bioware just does not listen to their player base. The continually roll out changes that are neither asked for nor required. I also agree that they do not even play their own game in a competitive atmosphere. They may test things on their little protected server but if you throw them into a 50 rated as a dps sorc/sage then they would have a rough go of it imo.
Balance forum posts are not useless; the forums are here for that. Unfortunately, as in any game, the overpowered classes watch carefully for any threads that point out the discrepancies among classes and they always make sure to enlighten us with their counterclaims. It is akin to professional athletes who draw fouls with bogus flops in order to fool the senior-citizen referees. They know that they are overpowered and they just want to prolong their free, skill-less ride. They get on every balance-request thread and leave 'QQ' or 'L2P' comments. But can we blame them?
It can all be solved if the developers would just play their own damn game, as each class and in a truly competitive environment.