I was on the fence about Farrell coming into the season, and this season hasn't really helped me in deciding which way to lean with him. With all of the underperformances we saw the last two years, I would agree with you in terms of a general sense that something is amiss with his managerial skills. OTOH, the players seem to really like hiim.
As far as his in game strategy goes, I haven't seen anything that glaringly bad. I know many disagree with that.
As far as having success with past managers, IMO, Tito is the man. It was a sad, sad time when both Tito and Theo were let go after the 2011 season.