In fairness, if you're going to put in a lacklustre performance it may aswell be in a europa group stage that you've alredy qualified from. Didn't watch any of it so can't comment on the performance, I was just surprised Arteta played such a strong side in the first place, and then that such strong side lost.
Arsenal weren't good last night, like you say, not a bad game to do it in but it now means they can't afford to slip up against Zurich in their last game, so he'll have to go relatively strong.
Arsenal haven't actually played well since they played Liverpool, they've played 5 games since then. 2 narrow Europa League wins, 1 win against Leeds that could have been dropped points but for a penalty miss, a draw v Southampton and last night's loss.
I think the World Cup break will come at a good time for them.