Indeed Mikel Arteta cannot sit back without any worrying because still there is many clubs that are capable of winning the title like they have potential. It's is obvious that Pep Guardiola has no longer here to compete with him but I think his successor Enzo Maresca can also give a hard time to Mikel Arteta.
Thus far other team are also looking good such Liverpool, Chelsea, Manchester united etc. All of them are try to rebuild their team with new signing and even the 4 star team are also preparing for league battle. So competition will be bit hard like only Arsenal will not be in open track. Other team will also try to tussle for title.
You have made your point, but I don't think that's the case because all other top teams are nowhere near the level of arsenal currently, unless their is a massive improvement from one of these top teams, because arsenal may run away with the title if their is no serious challenger.
Manchester City you spoke of are shaky, and they largely struggled against Bournemouth, so with what I saw on their opening day fixtures, I don't think they are ready to compete with arsenal for the title, Chelsea, Manchester United and Liverpool may all be scrambling for a top four place, unless their is a massive improvement from any of these teams, because as it stands now, arsenal is my best bet to win the English premier League title.