There are various more subtle approaches - for one thing, hitting a certain gong not far away gets some of the DKs to split up (so I read here - I haven't been able to ring the gong regardless of what weapon I had equipped).
With two warrior build characters I just charged in, attacked one DK at a time and continued until all were dead. That worked fine at the cost of a few healing potions, which are not in short supply under 1.42. Even a mage-build should be able to survive one or two blows and be able to suck down some potions if you hit the spacebar fast enough. You can have your primary tank take a regeneration potion right before combat starts to get a few seconds of hit point increasing - that may make a difference.
