Best survivability: Sage/Sorc, due to force armor, force speed, knockback, etc.
Best throughput: Sage/Sorc, again. They can put down stronger heals faster and for less cost than both other classes.
Best sustain: Sage/Sorc, because once you get the proper talents consumption costs nothing but a GCD, giving you infinite resources without the caveat of having to carefully manage their regeneration.
Best AoE: Sage/Sorc, absolutely without question. The 31 point talent is unbeatable. Heals for more than the other AoE heals AND has no target cap, meaning it scales better in operations as well.
Best Mobility: This is the only category the sage loses in, because Scoundrels/Operatives can cast 2 of their three heals while moving.
Best Utility: Debatable, but the Sage/Sorc certainly is at or near the top. Interrupts, Stuns, Knockbacks, Shields... they have a huge kit and a bag of tricks that rarely runs dry.
Bioware gave too much tools to them :/
And they have unlimited force thanks to consuptmion with med pack.
The winning rate depends on how many sorc/sage in warzone.