As someone who really, really, REALLY likes Zilean as a character and champ...
PLEASE stop talking about reworking him.
Every time someone mentions a rework, I just cringe so hard that my teeth phase into each other and become a synonymous row of teeth.
Change his passive if you wish. Heck do I care about it?! Just DON'T touch his QWE or R.
Every time a post about Zilean pops up, I'm like
http://25.media.tumblr.com/tumblr_m60qpaqNR51rwojgzo1_500.gif