I'm not sure Nog would submit him, Mir has great ground skills and is a very big athletic guy, Nog might choose to stand like he did against Herring.
I would have to pick Nog, especially over 5 rounds, but if somebody is going to sub Nog, Mir is the style of grappler to do it; he is big, strong, and good with leglocks, which Ricco subbed Nog with in ADCC and Barnett almost did in their first fight.
Good call, beebs. I still think NOg is too seasoned for Mir to sub him - but you've brought up a great point.