Glyph Devestate over blocking or Last stand and morrowgar or putricides 251 weapons and you'll do the same. You also have a survival Prot spec. Deep wounds, especially with TC in AoE gives you some nice additional threat, but that's a personal preference issue.
I'd suggest taking those 2 points in cruelty and putting them in booming voice. an extra crit, on average, once every 50 swings (though it's RNG so it could be 3 times in a row then not for 300 swings) is less useful than a longer demo shout/commmand shout, which free up more CDs for your threat attacks (not many in the case of command shout, but over a 10 minute fight that a noticeable number more for a longer demo shout).