Now you're inventing spells on the spot and diminishing some of the most powerful mages in the setting such as Corypheus and Orsino because they can't do the spells you just invented.
Ok, listen, I'm going to take my time to explain, take the time to carefully read and understand. Komandor this goes for you as well.
Everything so far for me indicates that using magic works exactly like using ones muscles, so spiritual muscles if you will.
We have spellpower which is the indication of ones pure magical might, so a mage that has very high spellpower is an equivalent of a person with big muscle mass that can lift very heavy objects, a guy who can fight with a big sledgehammer.
We have willpower which is an indication of mages mana reserve, which is mages stamina, having high willpower for a mage is an equivalent of person that can jog for a very long time, or a person who can swing their light rapier for a very long time.
Both of these together in unison make a very good ''physical'' condition and foundation for casting powerful spells and casting them a lot and often.
But that's not all. There is such thing as martial arts, an art of using your physical condition to the fullest potential. Often martial arts makes use of a weaker physical condition to such an extent that it can be more effective than greater physical condition, and to be a professional warrior it's not enough to just have great physical condition, one must also know how to fight properly and effectively and have right experience that is sharpened through years of training. Same goes for magic. Circle or non-combat oriented mages to me are an equivalent of people that go to a fitness gym. To be a real battle mage you must have not just the knowledge of magic, but also the knowledge of how to use it effectively, and years of training and perfection of these arts.
Imagine a mage that doesn't just learn how to conjure fire and how to cast a fireball, but goes to the shooting range every day and casts set fireball over and over again until they can't cast anymore, and does it for years until it becomes an instinct, until they can cast that fireball by any day any second without even thinking about it, when casting becomes as natural as using any other muscle in your body, like walking.
Then imagine said mage striving to make said fireball fly faster, so that it would be very hard to dodge even for fast moving targets, and working to understand fireball physics, direction and learning to improve accuracy, then adding some extra juice to the fireball so that if it is for example blocked by a shield it explodes and engulfs the whole enemy in fire anyway. Then imagine said mage training against actual opponents for a few more years and learning how to deal with everything that might happen on the battlefield, and finally said mage is going to go to war and put all these skills to serious practical use. THEN and only then, you have a real Mage ''warrior'', that knows how to fight with magic and knows warfare.
Where can you find these mages? Most definetely not in the circle, they don't train killing machines. You won't find them among the dalish, and not even among Tevinter mage nobility, it's not the mages like Corypheus that sit in their glittered chair spitting orders at slaves and enjoy their luxury. One of the places I can think of where such mages could be found are Tevinter battle front lines.
You say Corypheus is strong, and I agree, he is strong no doubt, but I also think that you can find quite a few scarred, battle hardened Tevinter mage war veterans that will wipe the floor with Corypheus. The kind of mages that live war everyday and kill Qunari by the hundreds.
Even if they wouldn't have the natural talent of Corypheus, or his shear power level, they would defeat him through through their experience and hard training. They would blast him fast, they would blast him hard and they would blast him just right, and they would stay calm and focused while doing so, and have appropriate defense that would work like on an instinct level like an eyelid protects an eye when it is in danger.
Corypheus to me is like a big jog bully that could no doubt kick the butt of a regular person through shear physical strength, but that doesn't mean that said jog could easily defeat a great martial artist, even if that martial artist has less raw physical strength. Circle mages are also akin to big muscular barbarians that are very effective on the battlefield just because of their overwhelming might compared to a regular person, but they are far from trained warriors.
Edit: Are these mages Gods? No.
Can they still be taken by surprise or be exhausted due to being overwhelmed by great numbers or other stress? Of course.
But a might of a battle mage is far greater than any mundane warrior can achieve.
Think about this, and tell me where my logic is flawed.