I've noticed what seems to be an error in the ability cooldown timer with my deathknight. It will sometimes think scourge strike has 5 seconds left on its cooldown when really it will only have a second or two. So for example, it will begin counting down from 5, 4, then refresh at 4. I assume the existence (or near existence) of a death rune will be at the heart of this issue. It's an annoying bug because it causes me to stare at scourge strike instead of believing the timer that comes up on it.
Try using the following rotation to replicate the problem.
PS-IT-BS-BS-SS-DC-HoW
SS-DC-SS-SS-DC-(DC)
IT - Icy Touch
PS - Plague Strike
BS - Blood Strike
SS - Scourge Strike
DC - Death Coil
HoW - Horn of Winter
( ) - Indicates you should use if possible
Spec -
http://www.wowhead.com/?talent#jfVMM...ux0uIqo:LsbMmV
Glyphs - Glyph of Dark Death, Glyph of the Ghoul, Glyph of Icy Touch