I said "But making them completely dependent on healers is just a bad idea." So to counter your horrible point.
Most DPS have self-heals/Defensive CD's to protect themselves if The Tank or Healer momentarily stuffs up.
Most Healers Have Defensive CD's and can keep themselves alive through Self healing if The Tank stuffs up.
Making it that Tanks who are MEANT to be the best at mitigation/avoiding damage should not be able to maintain themselves for a period without the constant application of heals is just bad design.