Mage duels, dispels, and counter-spells have long been a Fantasy standard; does not mean they will police themselves. Such displays of power may even lead the non-Mage citizens to fear such power; hence the call for those like Templars.
As for the topic, if one does not like certain effects and abilities for their non-Mages, don't select them. Or if one must select one as a pre-req, simply choose not to use it. There are plenty of other abilities from which to choose.
Non-Mages fear powers of Mages also a cliche in Fantasy standard, "people fear something non-ordinary/unusual/unexplained" and "people fear what they don't understand" is a common trope and almost a stereotype...human are actually not that stupid, but continuous brainwashing by medias, religious leaders and politicians with their own agendas lead to bigotry and that what makes things happen...or else there is no issue because human are able understand and learn differences, that what makes us human a human and survive million of years living on this planet...The stereotype must be kept alive for reason, for control...human are controlled through fear.
People with power will surely abuse power is also a cliche and stereotype, a Police officer will not just shoot people because he/she have a gun, the same logic apply to people with magical power on their hand. Of course some powerful people will abuse power, but not all and not all who have power have the same mindset. Just because you have power, doesn't mean you want to abuse it just because you can. So, in this context, not all Mages will want power over people by abusing their magic, not all Mages have the same mindset, and some might disagree with the abuser. in short, Mages can police themselves, the same way normal society policing.The word "police" itself comes from "policy", it depends on who make the "policies".
As for the topic, sadly Dragon Age is hybrid-friendly, as many modern games nowadays, almost everything have magical effects, it is because Dragon Age is a meltdown game that use the old D&D mechanic, to please the new generation crowds who love something that look "awesome" and "cool" fast combat dealing tons of damage, not the clunky boring hack and slash...most of medieval-fantasy RPG characters now are magic-hybrid in their skills