malz brands and zyra have a problem with scaling
if I have to put a finger on why i prefer to play these champions myself in the botlane is because
1 they have very poor matchups in general when they go mid.
2 it doesnt feel rewarding to buy ap items like deathcap due to scaling that's off, take 
for example it feels VERY rewarding to build deathcap.
3
are core on all three and rylai is basically a mage support item.
so they are in fact supports with high base damage yes. but that's also because they dont scale as well with ap as other more traditional mages. as such their prime role naturally will gravitate towards botlane.
remember when she went support? and riot increased the ap scaling and lowered her absurd base damage? yea that actually fixed the issue.
