We don't need a DM mate. Playing 3 at the back that role becomes the job of the central CB. The player in the traditional DM role should be a release valve. Gets the ball and quickly dstributes it. Gundogan and Silva would be excellent there. If we were a back 2 rather than a 3, then yes, you need someone with a bit more steel, but we need a Modric player in front of Stones rather than a Fernandinho.
He simply isn't up to playing the role. Not a great mover without the ball, and he's jamming up the lane in front of him. Fluid movement is exactly what's required in there, and unless he has the ball then Dinho just camps and waits for it once he finds space, but in this system his role is to make space by moving, not be in that space.