How can you say that marchisio didn't pass well? He had the highest % completion in the team tied with Melo at 85%. If anything, that was his strongest attribute this season was his ability to complete a pass and not lose it or result in the team losing possession.
When we brought Melo we had a completely different formation in mind with Diego taking the main attacking role for the team. Then, that failed and Tiago was no where to be found to be the "passer" we brought over Aquilani to fill the passing void which he failed at too. Melo was brought to destroy, nothing more. What about Melo does not indicate what his job would be whether specified or announced? His role is a DM, he isn't mean to push forward in attack, he isn't mean to be a deep lying playmaker, he isn't mean to unlock defenses with his passing, no his only purpose is to protect the defense and breakup play...and aside from the obvious (which he usually does well) is complete the passing when he doesn't try and over complicate it.