There is no problem with the circlet. It is not a balance concern in any way.
I can read all that but I still think this item is too powerfull right at the beginning of act 1.
According to me we shouldn't be able to build our lvl 1-4 characters arround such items and an EK should never be as (more) efficient with magic than a regular wizard that is going to invest its lvl 4 additionnal ability points in intelligence to reach 18.
But you're right, this single item is absolutely not a balance concern.
