Of course the coaches are better in the EPL than the A-League, but so are the players.
Guardiola along with Anceloti are probably the two best coaches in the World, but they also coach the two best player rosters in the world.
A fair comparison of one coach with another coach is one done on a like for like, in the same league but also with the quality of players they have. No-one could seriously say Spurs playing squad currently matches City or Real Madrid's squads.
Brisbane and Yokohama were not in the top 3 clubs in their leagues when he took over. Nevertheless, it took him a season but he won trophies and changed the club culture on the way.
Celtic was a toxic place when he arrived. Nevertheless, it is still Celtic, they are perenially first or second and have the biggest budget. So when given that environment what happened- he won 2 out 3 trophies in his first season and 3 out of 3 in the next.
I believe his IS a good manager, but the question has always been given the leagues he has coached "How good?" When given the cattle, how far can he go? He has not got the cattle to vie for top 3 this season, so the answers are still up in the air.
It is concerning -and he said this- the team should be finishing the season better than it started it, but in fact its not. That's not what has happened elsewhere he has managed. Has he "been worked out", is something not gelling with the players? We're all guessing at this stage.
Barring a catastrophic end to this season-which is possible with the fixtures to come - he should get another season