If I am honest I don't think you have had that bad a season, as someone else pointed out you were expected to finish 4th or 5th in a battle with Spurs (but we all know what happened to their season), as it is, your 3rd, still mathematically in with a shout at winning the league and have only just lost ground on the front two, and we are 5 games from the end.
Personally, you lack strength in depth. If you look at Man United and Chelsea they are full of World Class players, United can leave Rooney and Ronaldo out of a Champions League tie and still win the game, and when they do leave them out they still look really good. Chelsea have a vast array of talent (but we all know they had to buy it). I don't see that with Arsenal. If you leave your two best players out (this season Adebayor and Fabregas) you cant see an ideal replacement and thats the problem, oh, coupled with the fact you always try to score the perfect goal.
I agree, since the Birmingham incident you have quite been the same, and that incident is enough to knock players, but that excuse cannot run forever, and the players should be able to put that behind them. However, more recently its fatigue thats costing you, due to your injuries and lack of squad depth you are unable to rest players and thats showing, you have been heavy legged come the end of all the Liverpool games.
Its ok saying you have all these young players, but are they the answer? I don't think so, they lack experience in the league. You can argue that the Carling Cup has given them first team experience, but after the 5-1 drubbing by Spurs not many have featured since, and those that have don't appear to have recovered.
Now, the first team. Gallas isn't as good as its being made out. On SSN last night when they were evaluating the Arsenal performance, it was Gallas they were singling out, and it wasn't his only bad show. He was run ragged at WHL in that drubbing, pulled apart by Chelsea at the Bridge and thats just two recent examples. And then there is Senderos, don't think I need to comment on him really.
Up front you lack support for Adebayor, who to be honest has surprised me this season. I didn't think he was a 20 goal a season striker, lets see if its a one off or not.
Basically, you need to strengthen in the summer in a lot of areas and not seek to rely on the youth products, yes they may be class, and could do a job, but until they do, they arent going to be the solution.
*Now, I am a Spurs fan, so hopefully you will see this as friendly criticism and not as a dig. Whilst personally I like the fact we have won more than you for a change I am a football fan as well.