Support: Rushing Morello's + Athene's = Win?!

So I've been building Morello's straight into Athene's after support core recently and wondering what part of that combo is helping my gameplay/win rate. I'm thinking its mostly the 40% CDR but still want to check for other thoughts.

Edit: It seems the 20% Mana refund on assist helps when going oom in team fights, that and I play a lot of Sona, Karma, Lux so Athene's shield/heal buff is also a thing.