Zilean needs to be balanced

I've noticed that Zilean's Q does a large amount of damage come late game, but that's not what has my attention. What irritates me is that his cooldown reducing ability allows for him to never be killed in laning circumstances, and prove very difficult later in game as well. Considering this ability reduces his other cooldowns by 10 seconds, it's not that bad. However, at max rank the ability itself has a cooldown of roughly six seconds, give or take CDR masteries. This is almost a two to one ratio from provided CDR to the cooldown itself. This would allow the cooldown of his ult to be reduced by ten seconds once every six seconds, reducing the overall cooldown by roughly 60 percent, without CDR items. This combined with Guardian angel is equivalent to one extremely irritating champion that just will not die. I think it would only be reasonable if either the CDR ability didn't affect his ult/ affected his ult in a smaller amount