The main reason why grant has (apparently) improved is down to his CM partner. Last season grant sat back and the midfield was built around Maccas strengths of whinging at the ref and blaming other people. However he didn't have the drive to do that last season (and if he wasn't getting paid that explains it, even if IMO it doesn't fully excuse it).
Easton generally sits back (although last night granty would allow Easton to push forward at times). Grant generally had a free role, and this played to his strengths, because he can shoot and can pass, he can also dribble which really infuriated the immobile Bradford midfielders.
The secondary reason, as you allude to, is that defensively we are more assured. Moshni likes to get tight and to step forward with the ball (a la Rio Ferdinand), and so having grant next to him is pointless... Let moshni play a forward ball to grant or Easton who are already 10 yards further up the pitch. Gilbert was exceptional last night, which was good because Hall hasn't got a defensive bone in his body. Moussa isn't a defender, but our left side was a weakness with young fullbacks generally so granty often got pulled across to help out.
We're playing a rather flatter midfield 4 this season. Part of the reason we can do this is that our central midfielders are more mobile than we are use to in recent years as Maher couldn't and McCormack seemingly unwilling to run. One of the things that I've enjoyed about this season was how our central midfielders actually get into the box. It took something like 45 games last season for a central midfielder to make those types of runs, yet Easton has already scored from that type of situation and Grant has been getting forward well as well.
Moshni is OK on the ball when he's given time, but looks uncomfortable with the ball at his feet when under pressure. Centre-forwards will be told to pressure him.
Grant also played on the right-hand side of midfield a fair bit last season, especially with JFC in the side, but I suppose this is Moussa's fault as well. FWIW Moussa is far, far better defensively than Hall.