So, the DA cog gives you a tighter grip on the Miche hub, but a Miche cog on a DA hub would be just a bit loose -- if I'm following all of this correctly.

I've been having something of the same issue: I have a Miche hub and DA cog. The DA cog was a tight fit, but it did get on there without forcing it and with no obvious play. I haven't tried this (Miche/DA) wheel out on the road yet (I got a super deal on a Mavic Open Pro / Pro Max wheelset from Dixons in Brooklyn and I'm running that at the moment), but I'm really itching to try out the Miche hub. Should I worry about the DA cog or plunk however too much $ on a Campy cog? Or does Miche still offer their non-quick-change system cogs?

im about to do this combo, hope it werks ;)