I completed both Blood Harvest and Feast or Famine with pseudo tank formation (healer+defense buffer but no tank). It would be slower than usual but it's stable and with enough DPS, you could leave it unattended
The second strategy is by using RoboRabbit to store DPS. With him storing DPS, you could click the monsters to kill them. No tank, healer nor defense buffer needed. This is faster than above but you must be active playing to click the monsters