Riot I did an experiment on balance
I went outside and grabbed an evergreen tree branch and had my friend whip me with it repeatedly for a few minutes. To be honest, it was uncomfortable and itchy, but it certainly wasn't painful.
This makes me really wonder why Zyras base damage is so high. Plants, quite frankly, are not that painful and I'm having difficulty seeing the correlation. Maybe your balance team should go outside into nature to get some more inspiration on this menace of bot lane.