How about this nerf to pteranodons: Nerf the build speed
That way, it takes longer for the coronia player to amass too many pterandons in which they just roll over any sort of vehicles. With a build speed nerf, even factions with lackluster anti air can keep up with enough AA to combat the coronia death cloud of pterandons.
I haven't really played many games against coronia as people are decent enough to not use it seem to know it is OP, but with all this fuss about this unit I think nerfing the build speed would be good as it doesn't take away the unique properties of this unit (eg, AOE, anti-tank, flying), but it makes it harder to spam.