I really think we need 2 DMs. Over the years we have let go of Diarra, Gilberto, Flamini, Denilson, Song, Coquelin (Diaby is also a write off). Who have we brought in to replace them? In 10/11 we played Jack in a deep role although I don't think Wenger sees him there anymore. As for Arteta, he has performed admirably in an unfamiliar role but he is certainly not a long term fix.
If we do sign Fellaini (I believe it will happen), what happens if he gets injured? He has suffered quite a few nasty injuries and once you put on the red and white the likelihood of you picking up another injury increases tenfold. Wenger admitted last Summer before Song was sold that we were 'short' in his position. Since then he has been sold, Jack pushed further forward, Coquelin is gone and even Wenger has to believe that relying on Diaby is suicidal. So if we were 'short' then, what the hell are we now? We need two holding players, Fellaini and I would also like to sign Kongdobia who has massive potential and considering his age may be happy to be more of a squad player for the next year or so.