In all honesty, we really don't know the criteria, for them putting people into extensive screening (well apart from if you are from the middle east, which is well known), usually its a random selection so pray you aren't part of that. The most important thing is that you submit all documents needed and provided them as accurate as possible. I'll give my ongoing process as an example.
Submitted my application Feb 3rd with AOR on the 4th, got move to IP2 around the 27th of Feb and the my application got stuck. ordered GCMS which came back about 3 months later, only to find our i was in Review required. Submitted a letter of explanation regarding the issue, and then criminality was passed in August (6 months after) then silence till Dec, where my Spouse was asked to do a re-medical. ordered GCMS report once every 2 months and it always said, Eligibility - RR; Criminality - Passed, Security - Not Started. and by 8th Jan. my application was approved (meaning security was a matter of days). Do mind i currently live in Canada, but i also have an extensive travel history, Spanning Europe, Northern America, South America, the Middle east, and Africa. so am pretty sure it shouldn't matter.
Am now currently in the waiting list for "Ready for Visa mail".
Best of luck and I hope yours isn't as much long as mine!!! Close to a year now...