Minimum level for aegis of the hearth?

I didn't note the page at the time, but the Waimee chapter in antagonists clarified that it does.

And I agree, having the aegis need penetration is THE reason to have all the magi collabote through WC to cast it, which, IMO, is more mythic. Otherwise, you just handle it to your ReVi specialist while his covenant mates sit on their collectives asses.