Lets be clear all he said is that he has been tanking Nax and heroics in a ret/prot hybrid build and that he is not having any issues with the loss of avoidance talents. He is not telling us to all spec like him nor is he saying that his build is better for whatever level content is "hard" for you. Honestly he is probably right 98% of the time the extra dps from being ret will be more useful than that extra edge in survivability. Heck it makes you a lot more useful if you are an off tank in Nax as you can dps much better when you are not needed to tank.
TL:DR It is a reasonable option for farm content and that is all he is actually saying.
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