Tanking Death Knights, don't buy those Glyphs of Icebound Fortitude just yet. The glyph is meant to make Icebound Fortitude a little more potent in PvP, where a DK is unlikely to have much defense on. But apparently (and this is news to me), there was a bug where it was giving benefits even to def-capped DKs, and thus many people were picking it up for PvE use.
As always happened eventually, Blizzard has spotted the bug, and they're going to be hotfixing it soon. The glyph will still keep its intended effect; PvP DKs will not see a change, most likely. But now I'm curious: what was the glyph doing for tanks? Was it adding 10% onto IBF at all times, or something?