Lol. Where do these armchair generals come from?
All classes that can tank have the majority of their damage mitigation locked at level 40 (plate and dire bear form).
All melee suffer with hit and resist issues (except human Paladins specced into protection, which is a whole different discussion) leading to times where threat is lost from RNG and nothing to do with dps.
All classes are specced dps unless you are leveling a very specific way (such as in a group or pure instance leveling).
When leveling, your gear likely stretches across 10 levels of various upgrades and random drops meaning your armor and health are not ideal.
When this is the situation, when playing defensively isn’t ideal, then the idea is the best form of mitigation is kill as fast as possible to minimize damage taken.
That’s why spell cleave and melee cleave are a thing.