At first, I was commenting on Waxsw's suggestion, but I might as well comment on how the Sage felt VS. the White Mage for the current 4 mans.
AoEs do feel a bit different for both. WHM can place Regen on the tank and spam Holy with Assize in between. The 3 stuns on the enemies pretty much offers enough mitigation with high DPS present. Everything is almost dead when they become immune to the stuns. SGE instead uses Physis to increase heals, pop Haima / Panhaima with the Physis buff, then demolish the pack with Phlegma and Toxicon. I know Waxsw disagrees with the Diagnosis shield making addersting procs damage neutral, but it feels like I can kind of do that for AoEs currently. Dyskrasia only starts to get used when the enemy count drops to around 3 ... Which is a very small time frame.
For single target bosses .... Pretty much the graphs that Waxsw linked is my feeling. SGE is another Glare Mage using a different name. The counter to AoE damage is Assize + Afflatus Rapture VS. Physis + Kerachole. Tank busters would be Regen + Divine Benson VS. Taurochole with Kardia mending the rest. Additional Aquaveil VS. Diagnosis shield if the tank is getting hit by a truck which is not often for geared tanks.