It was this distraction that cost Arsenal the premier league last season. At present Arsenal don't have the capacity to successfully compete in the premier league and Champions league and win both. If it was very easy they wouldn't have waited this long without the premier league and the champions league. Let them set a clear objective, if they are going for the premier, let them devote all their resources there and focus on it, then try and much as they can and get to the Champions league Quarter finals and exit the competition so that their attention will be fully focus in the premier league. There are many teams that are far better than them in the Champions league and it will be difficult to overcome all of them. But in the premier league they only have Manchester City to deal with because for two seasons now Manchester City has been the only stumbling block between them and the league, so if they can go one step ahead this next season without divided attention they will win the league, because Manchester City focus will be more on the Champions league this season.
Well I don't see why they should not compete for the two if they can. You'd have to agree that they did better than clubs who have been frequently entering the tournament. I mean, no competition is a small one and clubs like City who were able to win both don't have two heads, do they? You'd have to agree that Arsenal's ability to win titles doesn't just rest on the players but also on the coach and his mentality. We noticed some absurd selections Arteta will make in crucial games when in the first place those players aren't supposed to even be used at that time.
What I know is this season will not be an easy one. Many competitors for the title will rise in the form of Aston Villa, Liverpool, Arsenal and maybe Newcastle or even Chelsea, so instead of focusing their energy alone on the Premier league, they are free to set their sights elsewhere.
It will be like you are questioning their capabilities when you limit them to the league title alone.