The issues with Arsenal go much deeper than them covering weaknesses with new signings. Yes, you cannot argue against them strengthening significantly with the likes of khedira and Sanchez, two genuine operators at the highest level.
The problem though with Arsenal is twofold.
Firstly, they are the poorest of the top sides (the big five say) without the ball. This has been a common theme with Wenger sides throughout his reign really and was highlighted dramatically when the old back four he inherited left the scene. They are a forward thinking side with great movement but there are two sides to the game and they only excel at one.
The other issue with them is their mental strength and for me they are still lacking here big time. We absolutely battered them last season and Chelsea embarrassed them too. Even united beat them at home, they have a habit of capitulating and when you look at the squad, you’re asking yourself who are the leaders here, who'll drag the side through tough times? Wenger's sides have been found wanting at the business end of the season too many times, this won't change.