The failure is yours if you are not knowledgeable nor skilled enough to use the tool kit properly. In most situations I have no problem walking all over, any/all of the other classes with the defenses and mobility Ret has. If you perceive other classes to be "better" go play them. Ret is perfectly fine as is. Arms and Survival are far worse defensively then the other melee specs, though their mobility is slightly better, situationally at least.
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A different spec, with a different design. If you want the toolkit of a rogue, or DH go play them. All the tools a Ret needs are right there. It all comes down to proper use of abilities to counter the other specs abilities. If you are misusing abilities you can't expect to properly counter them.