Glyph of blocking is not going to make a substantial difference in your ability to survive heroic Deathbringer during frenzy. Making sure improved demo shout and thunder clap are up ( or their various clones vindication, frost fever, judgements of the just) near 100% will. As well as wearing your highest EH tanking suit.
If that is not enough use your CDs it is what they are for.
Oh and making sure he is low on blood power when he frenzies is also a good idea.
Army Strong = Two hundred thirty four years of tradition unhindered by rational thought