For the death knights at the fountain, you should be able to get just within range for the wand without triggering combat, and kill them that way. When you get close, move slowly; there is only a couple steps difference.
Other than that, just get your character with the wand close, uses Haste on them if possible, then summon something between the character and the death knights. Have your other characters move up and summon things, as well, as a distraction to hopefully keep the character with the wand from being targeted.
If particular death knights like targeting the character anyway, reload and target them first the next time.
