I can see how one who is specced as 31/0/10 (which I am currently trying for the first time, former Deception Shadow) can appreciate the 2pc survivor bonus. However I find that I cannot part with the 4pc Stalker bonus, it's just too good from a burst perspective. IMO it comes down to controlling your target vs. bursting your target. I have both sets so I may dibble and dabble into the 2 pc survivor set.