TL;DR, Agny boosts 2 unused spells from the past and there will be a new attribute that reduces meteor cast time by half at level 10. Theoretically with quick cast it should be 2.5 seconds to cast a level 10 meteor and with enough attribute and matk we should be able to hit the damage cap at 199k.
Prominence is extremely good at DPS check floors with frost pillar because you are almost guaranteed full hits from both flames jumping around.