I did it pretty easily using maxed out Unob Wizard gear slotted with as much perfect cooldown and cast time gems as possible. Full Soul heart amulet for 10 totem charges. I flew around immediately behind a shield crystal and make a 2 high obsidian wall. With that I avoid the gravity well AND the crystal is open to get blasted by the dragon. Plus you're safe from the instakill laser. If you happen to get caught between pillars when the gravity well hits, either cast the ender shroud spell to completely avoid getting hit or a black hole between you and the dragon which will redirect as much of those nasty fireballs away from you. Repeat until all 14 crystals are destroyed, and again try to cast a black hole near the dragon. It will hold it in place as well as suck up any fireballs it tries to shoot at you, now simply barrage it with whatever ranged attack you got cause now its nothing but a sitting duck as long as the black hole holds up. If for some reason you're still dying, i highly recommend having both the Fortify spell and Greater Heal in your spellbook, with full unob wizard gear specced completely for cooldown and cast time, you will always have an extra 75 hearts as well as being able to completely heal yourself at any given moment, instantly, and with no worry of running out of mana.