The issue isn't that you die and can't be brought back to life, it's that you die and everyone else lives. In a game with the Role Trinity, every job needs to depend on the others. DPS and tanks shouldn't be able to stay alive for meaningful periods of time without a healer's support; the times when they can stay alive represent a glaring flaw in the Trinity.

In most fights, DPS will end up dying to unavoidable damage, but tanks can (slowly) solo the majority of boss fights because their sustain is through the roof. Outside of double-pulls, healers generally don't have much of a job to do.