Making Kayle / Zilean, a bit more fair?
As of now, kayle remains a top lane bully, and an amazing counterpick for teams that spam R to win. cough assassin / all in damage champions
A reasonable change to kayle, would be to make the range on Intervention very short ranged, but increase it's duration.
Gameplay changes - this means kayle has to be next to you to ult you, leaving her in danger and forcing kayle to be a bit more on sync with her team. Rather than an "oh shit" button.
If the same applied to Zileans ultimate, he would also have to be close to allies. There seems to be no problem for Kayle and Zilean to get to allies, they both have speed up skills.
So Zileans ultimate would have to resurrect allies with more health.
This would make both Kayle and Zilean a better option for support picks, yet they wouldn't be ban worthy since their utility gets hit a bit harder.