Your current spec your running with i recently tried a version of that but instead of Blood/Frost i went Blood/Unholy.
My main thinking was i would get Spell Deflection and VoTW. However what i noticed was i lost a considerable amount of threat and only really gained a slight increase in surviability.
I mean i currently run with a 10/05/56 build and have no issues as of yet with threat.
The World of Warcraft Armory
See above for my armory.
In regards to your two specs you have listed as wanting to try out:
Killing Machine, rather wasted points there as you don't have Howling Blast. or Frost Strike, i think those 5 points would be better off going into Blood Gorged, which would give you more TPS than Killing Machine imo.
Also not a big fan of Sudden Doom myself, i think you would find something like.
Talent Calculator - World of Warcraft
Giving you a bit more TPS.
Unholy build i can see where your heading to pick up Frigid Deathplate, again KM is a bit of a waste imo. In terms or TPS not taking Blade Armour is a big TPS loss.
If you'd like to give unholy a go have a look at my spec, very nice TPS with a simple IT - PS - BS - SS - SS rotation and using DC and UB to dump your runic power.
Looking at your armory i think your Hit Rating is really low and that will effect your TPS greatly. Try getting that up.
I mean all in all theres loads of different specs out there, and they all have advantages and disadvantages over each other. The main thing i find is finding one that suits your playstyle, once you've got that stick with it and work with tweaking a few things here and there.
Hope this helps.