Figuring out tactics for spellcasters is always complicated by the need to assess the relative merits of their spells, which requires application of game-theory math along with examination of their action economy. I’ll start with the mage non-player character, basically a level 9 wizard.
Before looking at spells, let’s look at abilities. Strength is below average, Dexterity above average: a mage is a ranged attacker by preference. Intelligence is very high: a mage knows which enemies to target with which spells. Wisdom is above average: a mage prioritizes self-preservation. In fact, given the amount of training and education a wizard has to undergo in order to do what he or she does, and also given how squishy magic-users typically are, I’d say the mage has an above-average interest in self-preservation and will commence escape protocols after taking only moderate damage (reduced to 28 hp or fewer).