Viera damn it!
Still don't quite understand why you say Heit lacks positional discipline.
Getting involve is a must for DM. It's an important characteristic you'll find in Keane, Viera, Pirlo, Rossi, Essien and Alonso. DM is often use as first point of building attacking moves in modern football even though he's playing deepest in midfield. I have no complain if he stays deep and get involve there, which is what he's doing.