There are some differences with Ars Magica. The Forms aren't the same, and the logic behind the Arts are really differents.
The Arts in Ars Magica are Creo (creation), Perdro (destruction), Muto (alteration), Intellego (perception) and Rego (control/manipulation). With this logic, some spells can be combinaison of differents Arts or Forms. This seems difficile with Dominions Arts.
For the Aura, I'm totally agree, this is the dominions effects
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If I propose the PFPV system, it is because it offers a good system to hightlight differences between civilisations. And he have the advantage to be accessible for everyone, at the difference of Ars Magica. Furthermore, the PFPV system is a little less unbalanced in mage favor, due to difficulty to upgrade magical skills.
You have a great knoweldge of Ars Magic for someone doesn't play.
For special heroic ability, I think it is an interessant aspect in Dominions. All concept of Dominions is based on this. The Pretendant are sort of heroic ability. It is because they can convince people to believe in their godly power they became god and linked with their dominions. I think special heroic ability are of the same nature.