Just because we hardly see something does not mean it is any less heavy lifting, take Elisande for example, she froze an entire army in time. Something that baffled even the most senior of magi, or the rebuilding half of Silvermoon, it was done almost overnight, while the kirin tor took years to rebuild their city, despite it being much smaller. The most crucial part for any magi is first and foremost knowledge, you can be as powerful as you want to be, but if you know less about magic than your enemy chances are quite good you will lose and the unrivaled masters of the arcane on Azeroth lorewise are still the blue dragons, few and as scattered as they are.