Selfbuffed sustained DPS on boss dummy around 720 with 32.7 dps axe, 553 AP, 590 crit. But the main thing about this spec is that it has tools that can be used to overcome some of the difficulties of the melee unfriendly fights.

1. Mobility from Shadow Assault, Shadow Stalk and Shadow Shift.
Biggest loss of DPS is to not be in range to actually do real damage, you can probably parse a bit more dps with some spec on a dummy but it will take a long time to catch up if you lose even a few seconds of time on having to run to the target.

2. Burst
You have to be able to do a lot of damage during the times you can be in range. By using Shadow Assault or Shadow Stalk just before Scourge of Darkness you get a significant burst of damage. You also have Ebon Fury on 2 minute cooldown for some extra burst. The damage graph when parsing shows steady 600 dps, then bursts to 1000-1500 every 30 seconds for 5-6 seconds.

3. Threat
Shadow Assault and Shadow Stalk which are used right before SoD trigger the -50% threat from Stalker Phase. That means that when you do burst, you also reduce your threat generation and will not pull agro even if you get very lucky with crits.

4. Survivability
Self endurance buff, Exceptional Resilience for 6% less damage taken, Boosted Recovery for 6% more incoming healing and a bit more endurance, -15% damage from fire and death. It all adds up to not dying quite as easily. You could move the points from Exceptional Resilience to Great Fortitude also, depends on the fight which one is more useful. Shadow Stalk can be used to remove stuns, snares and roots. Twilight Shelter provides a very nice 8 second "oh ****"-button. Shadow Stalk, Shadow Assault and Shadow Shift can also be used to get out of range of something that is hitting you or away from ground target AEs and such.

5. Range
Ranged openers, fiery spike, fiery chains, twilight force. You don't do much dps from range but even the 250-300 you can keep up from range while building combo points makes a huge difference compared to not being able to do anything. I'm not saying this build should be used for ranged fights, but in a lot of fights there are very often phases where you have to move out of melee range for a while and doing something during those times is vastly superior to not doing anything. And when that phase ends you have full combo points, can shadow stalk right to the mob and do your biggest burst with scourge of darkness.

Rotations and other instructions
Macro 1: twilight force > savage strike > fiery spike
Macro 2: puncture > dusk strike > twilight force > savage strike > fiery spike
Cast a couple of fiery spikes after stealth opener. Use macro 1 when at 4combo points, macro 2 if at less than 4. Make sure you wait until you have 40 energy before using macro 2.
Use hellfire blades+smoldering blades if someone else is debuffing the target for increased critical hit chance, otherwise use hellfire blades+lethal poison. Or if you need to keep up a healing debuff then hellfire blades+fell blades.

Keep up fiery spikes all the time, cast it manually after using SoD or Annihilate. Not sure yet whether Annihilate is a dps gain or loss but I believe it's a gain so keep that up, it lasts 60 seconds so it's not a big deal to refresh. If SoD is not on cooldown then use Shadow Assault at 4 combo points to get to 5 or if Shadow Assault is on cooldown then use Shadow Stalk at 5 combo points, cast SoD, cast fiery spike and then proceed as usual. If SoD is on cooldown and annihilate buff is still up then finish combos with Blazing Strike. Try to make sure you have the +30% buff from heat retentiouse when you use SoD.

PS. Noticed during testing that shadow assault gets absolutely no bonus to damage from attack power. Its own damage sucks big time because of that but the boost it provides through the damage and crit buff for 10 seconds is where the real damage is anyway.