It should stay the way it is. Its perfect, they are not to rare and not to common. Plus riot still wants to make money off them.
Each key gets rarer from the first fragment you get for a month.
Here is how I understand it.
I dont know how rare the first drop is, but for an example lets say 50%.
Get first key fragment march 18th 50% next fragment 25%, then 12.5% and so on, until april 18th, when it goes back up to the original drop rate. Thats a fair system.
For the record, i do not know the drop rates or the amount of time before it resets.