@Riot, Would you consider creating a 15% CdR Tier for items?

There are so many sources of CdR at the moment, most champions can easily reach 40% CdR without sacrificing anything in return. Items that offer tons of damage also offer 20% CdR. I understand that they wouldn't quite be the same with only 10% CdR, so why not make a compromise and give them 15% instead?

Items affected by this would be Black Cleaver, Morellonomicon, Essence Reaver and Trinity Force. Essence Reaver would grant up to +25% CdR total with 30% Critical Strike Chance. Trinity Force would require a recipe change and build out of Recurve Bow. Instead of granting the Recurve on hit passive, it would gain 10 Attack Damage and lose 10% Attack Speed. I think some champions might even welcome that change, like Gangplank and Hecarim.

Other items could be "nerfed down" to the 15% CdR tier as well, should they prove too powerful in the future. So this opens up another balance option. Some items might even get bumped up to the 15% CdR tier, like maybe Zeke's Herald?

On the topic of Zeke's Herald (and this is a bit off-topic), if you gave Zeke's 15% CdR it would create a perfect ladder with Ardent Censer and Athene's Unholy grail: 40 Ability Power + 20% CdR, 50 Ability Power + 15% CdR , 60 Ability Power + 10% CdR. The Sheen items would also have this ladder, but to be honest, I would rather all three Sheen upgrades gave 15% CdR and the Mage/Fighter/Tank aspects were the reasons why you picked one over the other.

P.s.: If Morellonimcon had only 80 Ability Power it could keep its 20% CdR.