Wining against Bate Borisov is not the perfect standard to ti jugde Arsenal's level. They are clearely weaker this season than the past seasons. Mesut Özil is at his worst level in years. Snachez play like he does not want to stay. Chamberlain left with no replecement for him.
The difference between Arsenal and other big teams in england was really clear when Liverpool dominated them at the anfield.