I'd like to nominate Glyph of Icebound Fortitude. Being able to use IBF when you need to without a worry about RP can be a life saver. Granted, I'm looking at it more from a solo perspective since my 5 box group of DKs is only 61.

Glyph of Horn of Winter is actually very bad now. Not sure if it was fixed in 3.0.9, but in 3.0.8 if someone with the glyph had cast HoW, unglyphed players would not be able to cast it as there was a "more powerful spell active". This might not matter if all 5 have the glyph, but it gives no benefit except saving a GCD every 2 minutes.

- Souca -