The thing as always is that we need context, if we use TheDAS at least in the southern parts the problem is that mages are a group, historically they have been defined as a group. Even if they don't outright rule if they'd get to make a lot more pressure than anyone else. Our work conditions are bad? We go on strike, and it's not a case of being able to hire anyone else, you can't train someone to be a mage. They try to force mages to do something? If it gets to violence things are going to scalate very quickly, specially if a mage sees that he's going to get beaten to death and decides to let a demon in.
They could even just abuse the excuse of "if you make us overwork we get stressed, if we're stressed we may loose control. If we loose control abominations happen. So really, by having us work one day a week (and not from midnight to midnight) you're making people's life safer."
If we consider them in a setting in which they're integrated there's still a lot of tension. Simply put smith A has to spend hours hammering steel while smith B, whose a mage could use telekinesis to have a chunk of metal hammering or if he's skilled enough use said telekinesis to mold the steel directly. Smith A ends up being really tired and only being able to do X amount of equipment, Smith B can produce equipment faster with his magic, being able to cover more requests and deliver them faster, and even use the extra income to have lirium potions to solve that getting tired problem, something smith A cannot solve inmediatly.
If they happen to live in the same village that will create tension if not outright hostility because smith A cannot simply compete against B. "He could hire someone to enchant his equipment, or get a golem, or ...." With what money? If smith B is doing better. And that's the main problem, mages, except for the demons, have it easier and if they want to, they can cause a lot more trouble. I mean, for gameplay limitations we haven't really seen mages used their powers to their full potential (it's a videogame, the only thing that gets kind of close is pen and paper rpgs or books). No need to go as far as blood magic. DA2 force mage:
In the thread we had the dicussion of a group of people with crossbows. Well, say Smith A manages to get a group of people with crossbows to end smith B, unless he's paralized with fear (which being a civilian could happen, he isn't trained for that) just using the telekinesis he's mastered for his job he can pull a Neo and stop bolts middair, when not throwing his attackers around at bonebreaking speeds...
If things go well, mages have more than enogh advantages to cause friction with mundanes, if things go south mages have it far easier to enforce their will or defend themselves, and without any specific laws they have the same access as the mundanes to the tools and training for fighting. A soldier against a civilian mage will be decided mostly by the mage's psychology. A soldier mage should easily be able to outperform his coworkers. Simply put, to continue just with the possibilities of telekinesis, the mundane archers in the unit won't be able to make the arrows curve to hit targets, (and they actually need the bow, the mage just needs arrows.)
So, in the case of ruling? If ruthless a mage has it far easier, if not a mage will have it far worse, because he will have to act as a paragon. Just because of the What if? "What if Mage Ruler isn't as good as we think?" "What if he uses mind control?" "What if one day he snaps?" "If we go on strike in front of his palace he wouldn't throw a fireball at us, but what if he does?." "What if he's so wise because he used spells to memorize information?"
The problem is twofold when simplified like this. If integrated there will be tension and suspition against mages and, without getting to violence mages will simply outperform mundanes in their fields, and that will make them much prefered if not essential, and they moment they realize that they will end up abusing it. (Again, no need to go to extremes. Just think, if you were essential to your job because of how you were born, wouldn't you try to push for better work conditions, on the grounds that at best there will be two or three, much less experienced people that could replace you, and if not you can go on strike. And your coworkers? Well, they can't make that argument)