PVP can be a bit misleading sometimes as you can come up against players who have much worse gear than you meaning you have no problems defeating them while other times you come up against players who have the same or better gear than you and they defeat you easily.
In an environment where you have all players in full or mostly full War Hero gear, the shortcomings of a Sage DPS become increasingly apparent. A classes survivability needs to match their ability to output damage. I think there is a big disparity here for Sage's that doesn't exist in the same capacity for other classes at the moment.
A Sage can simply die far too easily given how much damage they can do. If another player decides to chase you, he will ineviatably beat you. You can kite, you can delay the inevitable but whether it is a Juggernaunt, Marauder, Pyrotech, Mercenary, Sniper, Operative, or an Assassin (or their Republic counterparts), you will be beaten.
There are four defensive options for a Sage when engaged by an enemy:
1) Use an instant Stun ability
2) Use another instant Stun ability (assuming you have taken the skill in your tree to make it instant. This can also be interrupted by damage).
3) Use a Knock back ability, which has only a fairly small knock back radius and is a horrible filler of Resolve.
4) Sprint
A Sage has limited ability to snare an opponent. One is available that can be added to a Sage's Force Shield, but given most Sage's are predominantly Balance spec, this ability in the skill tree is largely unused and given that it cannot even be intentionally triggered means it is hardly helpful. There is also the ability to use Force Slow.
For a Sage to get away from an enemy he basically needs all of 1, 2 and 4 to be available and even then, if the opponent has an ability giving them immunity to stuns, you are most likely about to die very quickly. A Sage needs distance from his opponent and given the various snares, jumps, stuns and grapples available to other classes, a Sage actually has difficulty in obtaining it. It's also very easy for an opponent to cast slow on a Sage and that greatly impairs any ability to kite or escape which are a Sages only hope when someone is chasing him/her.
There is often little you can do to actually survive getting picked out by an opponent.
The other problem is that while a person playing Sage DPS can top the charts for damage in a Warzone it's not by the amount that other highly skilled, highly geared players of other classes are able to obtain. In that sort of environment, a good player on a Sage might obtain an amount of damage for the Warzone that is competitive with the pack, but is far from the likes of a good player who is using another class who ends up top of the damage for the map.
It surely should not be the case that a Sage has lower DPS and survivability than other DPS classes. If survivability was meant to be at the low level it is now, then DPS most certainly needs a boost. If a Sage's DPS is at the level it ought to be, then survivability needs a boost.