I can understand giving Diaby and Rosicky contracts because they had the talent and potential to deliver if they could stay fit. Rosicky especially. He's the sort of player that could play that CM role Cazorla plays and has often come in towards the end of the season to bail us out when the Wilshere/Ramsey axis falls flat. Diaby also had serious potential for that role. No idea why Wenger didn't sign a CM with a similar attributes seen in these two.
Wilshere is a lost cause and hasn't got the ability the ability to be that sort of player. Time to let him go.