I've done some testing and comparison between my rogues and here is what i've been able to get.
Rogue #1, level 90 Draenor server
Rogue #2, level 77-78 Tichondrius server
Rogue #3, level 87 Arygos server (east coast datacenter IIRC)
I tested in several spots: right outside the Argent Vanguard, inside Scourgeholme, in Crystalsong Forest, and once on the border of Storm Peaks and Scourgeholme (on SP side). The main thing that seems to be causing the unstealth is phased areas and subterfuge. Now it may now even be specifically or only phased areas or subterfuge. Maybe the phased area and the spell have an attribute that causes them to conflict. And maybe other areas such as BGs or other spells (related to stealth, like vanish) have these same attributes. Maybe something like an internal timer? every couple of seconds maybe in a phased area or BG an internal timer is checked for certain conditions within that zone. Maybe that timer is causing subterfuge (and other similar spells/effects) to trigger or something i dont know.
I knew that Scourgeholme and the Argent Vanguard fort were phased. I took a guess and figured Crystalsong Forest, at least not the area i went to which was away from the big tree and the structures.
But here is a quick breakdown of what i saw. I took screen shots of all this stuff too, i just dont have anywhere to host it.
Crystalsong Forest & Storm Peaks (right on the border of Scourgeholme)
-subterfuge, shadow focus, nightstalker did not effect stealth (at least 2 minutes)
-remained in stealth no breaks
Argent Vanguard fort, right outside by the cemetary and Scourgeholme
-shadow focus and nightstalker stayed in stealth, no breaks (at least for 2 minutes)
-subterfuge breaks stealth every minute (exactly one minute)
-subterfuge occasionally will break stealth at random intervals, but this was rare, mostly it would stick to one minute unstealth
--random intervals usually happened once i got to the new test area. Very rarely would it go from normal unstealth interval of one minute to 20seconds, 30 seconds, then back to 1 minute intervals of unstealths
I have probably 30 minutes to an hour worth of time stamps. I got time stamps for when i arrived at a new area, when subterfuge proc'd telling me that i unstealthed, and 3 seconds later i would be visible. I even got time stamps of the stuff that didnt happen in Crystalsong Forest.
Edited by Rashoujin on 3/19/2013 12:03 AM PDT