Think problem Arsenal have is this season they are not a big draw (despite the new manager), Wenger always had a pull anyway due to his reputation.
Arsenal are in Europa League and every player they would usually want who will be moving this summer, will have options to play for clubs who are in CL next season.
So whilst their signings so far, don't look the best. I think the main thing is that they try to sure up that defence, will Sokratis do it? I doubt it. Although Arsenal's defensive problem was down to system just as much as anything.
Having said all that, Mustafi looks like an accident waiting to happen every time on the pitch. So it's down to personnel somewhat as well. The amount of unforced or individual errors players made last season was ridiculous.