Definitely the funnest character I've had the pleasure to run through danger room in a long time!
Build
Stealth: Make use of shadowmeld and obscuring to sneak past enemies for efficient objective clearing. Obscuring brimstone is really good once a heavy amount of mobs are rounded up to maximize output while invisible.
Single target: Both brimstone beatdown and x-slash are good options, BB gives a more reliable target lock that is helpful with bosses but can be bad in ground hazards as teleporting is random, I feel that X-S is better DPS.
Aoe: Use flash and grab to round up enemies follow by infernal and signature with death blow rotated in, Bamf bomb as you like.
Precision Fortitude Challenge 42
Precision: really good for X-S if mobs are stacked up with grab and go. Ultimate with precision affix is an instant boss kill if your ultimate is up :D
Fortitude: Patience is the key. Investing more points into shadowmeld can pay off with extra regen while stealthed.
Lightning Simplicity
Lightning: Heaven for NC, signature charges every 3 seconds for maximum carnage
Simplicity Survival Challenge 50
Simplicity: I also have an alternate build with Swashbuckler Slash in place of X-S (or BB if thats what you want to use). The added critical hit damage makes it have good damage output with affix bonus.
Endurance Simplicity Challenge 69
Endurance: Can be done but pretty slow if you have lots to fight. Consider careful HP management to still achieve survival chest with a few planned deaths.
Test of Skill/Tactics: I would not recommend these affixes as the signature is a main component of this character. They are still doable, but very slow and not really worth the time. Test of skill also further damages NC because signature is a big source of spirit return