Is there something fundamentally wrong with mages having some power? While Tevinter may severely restrict the rights of it's mundanes, this is not the case anywhere else that we know of.
Not if you're a mage. Most normal people in Thedas would prefer to run their own societies, it's why they rebelled from Tevinter in the first place.
Benevolent oligarchies are still oligarchies. And ultimately, they are mantained with the wellbeing of those who are in charge in mind, not those beneath them.
A good example of this is mage ruled Rivain. It may not be as opressive as Tevinter but there people are taught that Abominations are natural disasters and thus the best people can do is bunker down and wait for it to pass.
Meanwhile, in non-mage ruled Ferelden, people are taught that Abominations are caused by the acts of mages and demons that thus they bear a responsability to prevent them from happening because they can be avoided.
Evidently, Rivain's cultured is steered towards not turning people against their mage rulers even if this leaves them defenseless before Abominations.
Hence why it's important that non-mages rule their own societies. Besides the fact that they are the ones who bult those societies and thus they are the ones who should decide their fate, not mages.
Rivaini seers are respected members of the community who serve a function that only mages can (communicating with spirits)- they are not the rulers of the land. They pledge allegiance to Rivain's queen and look after the welfare of the community in general.
"All decisions involving the wellfare of most Rivaini communities rest solely with the eldest women. The most senior of these women are called seers, who freely practice magic."
A quote from "The World of Thedas." Seers are rulers, make no mistake.
Magisters would also say they are only looking out for the welfare of the community.
The Chasind are lead by their shamans, but I don't see any problem with this. They are said to lead largely peaceful lives.
If there is no problem with mages ruling over normal people, why would you oppose when it is normals who rule over rmages?
The Dalish mostly just want to be left alone. The clans choose their Keepers to lead because they respect them and it is tradition. They still consider themselves equals. You may remember this exchange between Master IIen and two of his apprentices:
"Master, what's wrong?"
"Nothing, d'alen. Pack those tools. We're leaving."
"But the Keeper didn't say..."
"Just do it. We're leaving. Whether the clan is or not is up to them."
The Casteless are also a tradition.
It is probably no coincidence that the elves who see magic in a positive light also live under an authoritarian magocracy.
And yes, it is an authoritarian magocracy. That exchange proves it. The Keeper was making bad calls after bad calls for no reason other than that she couldn't bear to be parted from Merril and there was nothing the elves could do to circunvemt the Keeper or remove her from her position.
All they could do was abandon the clan.
Have we ever seen a Keeper ever having his/her decisions overturned by a vote or something else from the others members of the clan? No.