Like Durance is wearing a robe when classic D&D usually has a priest kitted out in chainmail if not plate.

Whatever compliments his stats, I guess.

Depends on what you want to do with your character. Are you asking about Front line Priests? Or back line Wizards? A back line and protected wizard might do well unarmored to get more attacks/spells off faster. A front line melee priest however, will do well with the heaviest armor you can find and a shield to keep him safe.