@Meddler About Zyra...

Why not nerf her plant damage even more than what's on the PBE (currently from 24-109 to 20-100), and... make targets that have been hit by Zyra's basic abilities within the last X seconds take more damage from her plants.

Zyra's Q and E are both avoidable spells that can be dodged. This would add good counterplay and a nice rewards for Zyra players who hit their spells.

Then, you could be looking at AP ratios and plant HP later in the game (right now, her plants get one shot by melee champs when they spawn near them, even late game) if ever she becomes too weak.