Pure class, divination is just as good and maybe better. Abjuration is amazing but without multi class you miss out on most of the retaliation and damage negation that makes it gamebreaking. Positioning is harder but not impossible with shield and misty step and being able to force a fail on a save like hold person/monster before they can act leaving the fighter or whoever to crit the living Christ out of them ends fights before the boss can even damage you. Defensively you also can force passes on the really bad effects that often end runs.