Obviously, including a PDT set, but we're still asking because Stoneskin used to scale reasonably, whereas now it doesn't really even with extreme amounts of skill.
I don't know when as a mage my Defense is going to be very low (it should be at least 400) since we don't use Berserk and always have up Protect V. Aside from that the only realistic way to heavily boost defense is to eat Defense food such as Tavnazian Tacos, but this precludes eating "mage" food.
Of course, SE hasn't actually added anything for mages that performs on the level of a typical damage dealer's +25% attack food, so maybe your point here is that mages should be always eating defense food?