Esoterics on Treasure maps?

So I was doing a wyvernskin map since I saw you can get esoterics from it. I only got law. I do a dragonskin map, again only law. I did another wyvernskin map..for a third time, only law. Is there something wrong or is there only a chance to get esoterics because the patch notes didnt really make that clear.

You get esoterics on the rare maps that give ya like 5 HQ Crawler silks 5HQ Growth Form.Theta etc.. rare ones.