Affliction with the slow legendary and some levels of leech is really nice for islands, but is this the setup your using on island expeditions for your mage? If so, I would advise you to try a complete different setup when it comes to your azerite pieces, even if it means using 285 in all slots. For survivability you definitely want 3x Quick Thinking, the defensive traits you have are really lackluster, but arcane with 3x quick thinking has like the highest sustained selfheal out of all classes I tried at 110 so far(depending on the situation since it doesnt scale with target numbers, but even with one target you can get 6k+ HPS as long as you only use AE and AB). You still wont be able to endlessly pull, but for me it was like going from not even being able to solo some legion nhc dungeons to being able to solo most of them in hc and some on mythic, although it means sacrificing some damage.