Something I don't think anyone has mentioned so far, but the WHM can play a key role in helping the DoL do their job (which in turn helps the WHMs do theirs). Whenever you get a chance, try to toss a stoneskin on the DoL, and esuna them if they're inflicted with a DoT. The reason for this is that they can't do anything if they're inflicted with a DoT, unless they have stoneskin on so they're taking 0 damage. The same applies to DoH as well, but as they're not running around so much they are less vulnerable.