I think you can have success without a DM and formations like 4411 and 442 are effective this year but I think it is an important role to break up play without exposing your defenders and especially important if you play wing backs or attacking full backs.
I have started a save with my beloved West Ham and I am doing okay.
...But I am conceding so many headers especially from set pieces, however this has only just started to happen. I first noticed it when I played Man City I had my match prep on defend set pieces, I lost 3-0 conceding 3 headed...
Maybe pass completion depends on the league? I was Arsenal and was getting pass completion of about 80%, then as Schalke with similar tactics had pass completion of 88/89%