Topic Subterfuge Talent
Subterfuge is fine, really. It could have some potential PvP use for all specs, but Shadow Focus will still probably be more beneficial overall, especially for Assassination. Free Saps and Openers seem to be stronger in the long run, than getting one extra Opener (accounted for latency) and being Energy drained after.
Nightstalker is the odd man out on that tier, really. For PvE you don't need Stealth anyways. I guess it's somewhat useful when soloing stuff to avoid mobs, but other than that it's not on par with the other things on that tier.