I disagree with you my friend. her new passive is incredibly strong and having multiple plants out is much more powerful then before where you'd have 2 plants. So it having unreliability is one way riot gates it power. Trust me if you make it a better passive and more cohesive they'll have to nerf the plants ratio and duration even more :P
As she plays now she's basically ranged rng version of illaoi and i kinda like it. I honestly don't want to see zyra ever be a support again so please just leave her alone and wait abit before you come to a conclusion. Zyra is hardly the weakest mage of this update. There are people like Swain,Cassiopeia,Vladimir,Viktor,etc who more deserving of complaint threads. So please can you just wait a month and then make a complaint thread.
I'd say Zyra is one of the winners in the mage update next to Malzahar who is oped, Brand whose teamfighting got massively buffed,Veigar who can get even more ap now for doing what he basically already does at the cost of his old mana regen passive which won't really be needed now with the new mage items,Ziggs whose passive was buffed and was given a w gimmick at the cost of his ult 2x minion dmg.