The thing is yes, utilizing kiting tatics, LOS and knowing when to mez the opponent as full madness can net you a win against most players and classes. The problem lies in that it takes you so long to do this, so it isn't very practical in a warzone. I takes around 45 seconds to beat most classes as a dps sage. You have to spend the time kiting to make your opponent waste his cooldowns so you can burst them yourself. Sadly this lack of burst hurts the SAGE/SORC in warzones too, and there is no good force management mechanic for full madness.
Yes a sage can beat a sniper utilizing LOS in a warzone, but the amount of time you must spend to kill a sniper using this manner is ridiculous. Any class can abuse the weakness of the sniper by using LOS, but that far from means the sniper is bad class nor that the sorcerer class is fine because of LOS.
Why dies it take you so much to kill a sniper with full madness? They go down much faster unless they are engineering and have 2 shield probs available. Just make sure youndont waste your death field when he has entrench on, if he is MM he is likely to have siege bunker. Crushing darkness should be used after his shield probe expires.