I stumbled upon the Death Shepard herd on a road bifurcation, and this became the perfect choke point to hold them at bay, with Wyll's Hunger of Hadar spell. I only had to take care of the few that managed to slip around, while firing missiles and long range spells to the ones inside. When one did manage to move out, my monks "push flurry" or Lae'zels push manoevre or Wyll's repelling blast pushed them right back in, after they got a radiant shock from Shart's guardian spirits.
After my first (frustrating) time fighting the Death Shepards, I used Sleet Storm at the choke point. They kept uselessly (and hilariously) falling, as I picked them off with ranged. Combo-ing Sleet Storm with Hunger of Hadar is even better.
