Really not hard to get at all. Every time i've wanted one I've been able to find or make one in short oder. The problem is people like you being so impatient that you switcch back to base-Sins in about 3 seconds, when you "can't find" people to play Entrenchment with you.
The larger issue with Sins in general is that people rock up, see no one in the lobby (or only 1 or 2 others) and leave. Then someone else comes along. I have waited 1/2 hour at off peak times for a game, but could have had 2 10 players ones filled by the people popping in to see if anything was happening and then leaving...