If the mob is death warded you can always resort to the use of one of the disabling options I presented then melee them to death while keeping them disabled so they can't heal. Alternately you can use the healing curse option the poster above provided. Alternately you can use spells like firestorm, cometfall, etc but really you're best off meleeing a single trash mob and saving the sp. Make yourself a stone prison weapon from the attack on stormreach series and stone the giants then crit them to death.