Also late into this. In our world (Morval Earth) magic is relatively common but “battle magic” is rare. We have a number of magicians each of whom is aligned to a particular deity and has a list of spells that suit that deity. So quite often the magician is of no great use on the battlefield with combat spells but may have a morale, healing or affect the battle indirectly by creating mist, rain or by cloud rolling. In some games the most powerful wizards spend their magic points trying to affect the level of darkness so that one side or the other gains an advantage.
We are heavily influenced by Middle Earth and Hyboria where great magic is more slow and elemental and low level magic is mostly about health (healing, easing pain), wealth (bumper crops, blight crops), weather (rain making, cloud rolling, mist) and so on. Battle winning magic is rare though we do have tactical battle magic (terror beams, blinding flashes, missile deflection).
So magic has a place in most of our actions and battles but it is seldom decisive.