What are the objectives of the changes for Zyra that just hit the PBE ?
After this patch 7.9, the lane bully support have been nerf due to the coming of the Doran Shield and its huge regen on the ADC. Even before, I think that Zyra was strong but not broken due to the nerf of the aggro of the plants.
But I can't really the nerfs coming on the 7.11 :
Plants - Plant Health changed from 4 to 2 Plant Spawn Rate (increased slightly)
The decrease of health of plants make it killable only by one auto attack from any opponents, and the decrease of the DPS
Rampant Growth (W) - [removed] no longer increases plant health by 10/20/30/40/50% [new effect] now causes plants to spawn 10/20/30/40/50% faster.
This change is make sense : it reduce the health of plants by 10/20/30/40/50% and increase his spawn frequency by 10/20/30/40/50%, the same amount, it is nice.
Stranglethorns (R) [new effect] Increases plant health by 100/150/200%
Imo increase the health on the ulti his kinda useless, no one attacks plants when he have been ult.
Sorry if there is thing that I missunderstood