Sometimes, especially at a wedding, DOF isn't the critical element, in fact you need larger DOF because there are more group shots, staged or otherwise. High ISO would be useful in the indoor portions of a ceremony, but even then, not all churches are dark, and these days, ISO 6400/12800 is sufficient, and the 7D2 seems to handle that pretty well now.
So if you are doing the portrait (just individuals or couples), the DOF might lend itself to the FF, unless you have a fast prime for your crop, and low light would lend itself to the FF, but in almost any other situation, the 7D2 should work just fine. It will be interesting to see if Mr. Ziser changes over from his 7D to the 7D2 for his wedding business.
Of course Mike has extensively more experience with weddings as its his revenue stream, so he can come in and correct me, as can others that shoot weddings as a revenue stream.
when I had my 7D, I could EASILY take a 135L and put the rt eye 100% in focus and have to middle of the head go soft.......when done correctly with the right lens, shallow DOF is not all that hard on a crop and you get very acceptable results