GSoA's are rare for a reason. The ear is the ultimate item on the server at the moment, providing a bigger bonus than RoA 1000 and more of a damage increase than grinding an extra ult weapon for your team. They shouldn't be common in any zone. By the time you finish your AA grind for the rings and then the 1 mil for the ear, you'll likely have found half of the GSoA for a complete earring.
Making a zone a GSoA hotspot would be a disaster for the new-player economy, not to mention it's already going to be harder starting off with the daily zones all shut down at the moment. People are going to have to farm SLS the old way
But yeah, your best bet is to slam Anguish with the hopes of finding 1 or 2 per day and some days 0. Look to buy them whenever you can. The ear grind basically goes like this:
Rank 1-30: "Man why is the price so expensive, this is fucking lame"
Rank 31-40: "eh price seems fair, not so bad"
Rank 41-50: WTB GSOA 15 MIL EACH AND YOU CAN HAVE SOME ESSENCE AND AA CRYSTALS TOO I DONT GIVE A FK