Once again, Zilean is left in the dust
There is absolutely no reason to pick him over other supports. With the Windspeaker's Calling mastery giving a boost to shields and healing, Riot indirectly buffed all of Zilean's counters.
He already fared poorly vs. tank supports, who could just shrug off his Q damage and engage on him anyway (e.g. Braum, Naut, Thresh, Blitz) but now that he's also weak vs. mage supports (e.g. Nami, Lulu, Janna, Raka) he serves no real purpose in the bot lane, at least until level 6 where he begins to show a glimmer of usefulness. Even then, his ult is barely enough to give him a niche against assassins. In literally every other scenario one of the aforementioned supports would be a superior choice.
The recent passive changes were nice and all, but Zilean needs a hell of a lot more than that to be viable. He has the potential to be a strong champion, but the situations where he is useful are next to non-existent. At this point I'm not even sure what changes could be made to make him more impactful in his main role.
As a mid-laner, his damage is far too unreliable and avoidable. He can't jungle, and he can't deal with the brawly nature of top lane. That just leaves his support skills, which are mediocre at best. I feel like the meta is always against him, and he's never been truly "strong", the way other supports have been strong in the past. What can we do to drum up some support for the old fella and what can we change about his kit to make him worth picking?