I will preface this by saying that I only read the guide itself, not the replies, so if this was already mentioned then my bad.
For Mystery Stalker, you do not have to find Azrael in that exact sequence and it can be done post game. I know this for a fact because according to your sequence I found him in the order of 3,1,4,2,5 and I did it during my post game free roam. I did also get the Catch! achievement.
As of 4/28/14 my Borderlands 2 trading post is officially closed. I am no longer boosting, trading, farming, etc on the Xbox360. I am entirely on the Xbox One now. If you want to play Xbox One with me, send a friend request with a message
to GT zI Drucifer Iz (those are capital I's).