Glyph pestilence to refresh diseases on your target as well as spreading them with every use.
As mentioned above, I always run to the boss, disease and pestilence immediately and then drop DnD.
Make sure to hit pestilence repeatedly since the mobs your targeting might die from white dmg before pestilence fires, and you really don't want to lose your diseases on 15 mobs at half health where you can't get your diseases up again.
And respec into perma-Ghoul, he'll chase down all the runners from a mass pull very nicely. Just take the tier 1 tanking talent from each tree and then go all the way to Ebon Plaguebringer, the one that gives you a third disease, you'll notice this a lot in bigger death strike heals.
Thats how i did it, with a DK around 4.3k gs, dps gear. Boosted RAF sets 1-60 in about 16 hours total, but that would be a lot faster with the gear i have now