Context of the nerfs for Bramble Vest?

Clearly, over the past 3 months, Bramble Vest has been extremely overpowered. Riot, having made no move to massively nerf the overpowered item for 3 months is clearly saying the item balanced.

> Bramble Vest

• Reflect damage changed to 10% bonus armor from 15.

So if the item was balanced, why was the item massively nerfed? If the item was actually as broken as everyone has been saying, then why did it take 3 months to nerf the item? If you could not recognize the item was overpowered anywhere between now and it's release (despite a lot of high elo saying it was), then isn't there a huge problem with the recognizing of issues and solving them (which is the same issue that occured with Ardent Censer and how long that took to nerf)?