well the cool looking armor from the trailers is the mage. And from personal experience, and I did get a sword staff with a hella amount of fire damage. Not sure if it's THE sword staff you're talking about though.
Having said that you could be a warrior and have the sword staff as long as you have its requirements [aka constitution or magic or willpower]. But that would be really, forgive the term, stupid since if you were a warrior it would still give you attributes to mage powers.
tl;dr you don't need to be a mage but you will only be able to truly use it to its fullest as a mage.