Have a cleric merc ready. Stand behind the mob you wish to kill, and fire off your biggest one-hit attack. For example, an SK should use HT, a monk use their triple FK attack, a wizard should use his biggest nuke, and so forth.
You will die a split-second after the damage lands. Your merc should immediately begin casting res, which you accept, then click Ressurrect in the respawn window. Now you have around 35 seconds to kill the mob before it can DT again. A mana user will need to use some form of very quick mana regen, and a melee will need to use a form of endurance regen, such as Respite to get going. I managed to kill the Overseer this way as a level 88 monk. :)

Efreeti Battle Axe
Efreeti Dirk
Efreeti Mace
Efreeti Magi Staff
Efreeti Scimitar
Efreeti War Axe
Efreeti War Bow
Efreeti War Horn
Efreeti War Maul
Efreeti War Spear
Efreeti Zweihander
Fine Steel Dagger
Golden Efreeti Bracers
Golden Efreeti Gauntlets
Golden Efreeti Greaves
Golden Efreeti Turban
Golden Efreeti Vambraces
Large Sky Pearl