Mutilate is the premier single target dps spec nowadays, especially on Murderable mobs.    It is also the "most difficult" of the specs to play (though it's really not that hard), but you get your high dps as returns if you can pull it off.

Potentially, this spec is also a source of 3% more raid crit from Master Poisoner, but most raids will generally have a Ret Pally or Elem Shaman, or both, providing it.   Mutilates are probably the worst source of it and should not spec for it unless really needed.  

IP / DP / Envenom

Therefore, the only spec for it currently is this 51/13/7.   If Master Poisoner is really needed, points should be shifted from Turn the Tables.    If you're not facing a lot of Murderable mobs, and want to min-max for that, Murder can be switched out for other fillers.    Though do note, Fleet Footed will not stack with Unholy DK's aura, and Quick Recovery can be very rendered useless through expertise.    So most likely, not much of a dps filler points if you move out of Murder.

Weapon wise, due to Focused Attacks and Poisons scaling, fast weapons recieved a boost in power.    Though do remember, speed isn't everything, just like Combat with Combat Potency, speed only gives a benefit, not an overriding rule.   You would main handing the Faster of your daggers, and offhanding the Slower of your daggers, finishers proc poisons which outweighs the *slightly* lower mutilate damage.

Glyph wise, there's not a lot of Mutilate glyphs out there.    You'd choose Slice and Dice and Rupture as the main 2.   The last one is really anything filler, nothing else helps with dps.

Cycle for Mutilate is more of a priority system.   Watch timers, hit the appropriate button to refresh the ones you need to.

1. Keep HfB fully stacked at all times (can be done in stealth, out of combat, on the run, etc)
2. Keep SnD up at all times you are dps'ing (start an SnD whenever)
3. Mutilate to 4+ combo points

• If SnD is low, Envenom
• Else if Rupture is not up, Rupture
• Else just Envenom til you can Rupture again

IP / IP / Evis

So another spec has been floating around now.   This involves 2 fast daggers (til 3.1), dual Instant Poison, which means relying on the raid (hunters) to provide the poison, and use Eviscerate.     So a bit more of a greedy spec, but supposed to be on par or above the old IP/DP/Envenom method.

The build would be something like this:  http://www.wowhead.com/?talent=fhxf0exoVboIzAo0xV0hZxb

And your third glyph would be the Eviscerate glyph.

Cycles are pretty much like before, but you're more likely to land 5 point finishers rather than 4+.