That's great to hear that you got it working, Califdan.

As a datapoint, I recently did a Pi2 test and installed a stock image, the octoprint source and mjpg-streamer via git and then added enough service files to get the webcam and flask app to start up. I had to make one change for the USB camera to make it work in the mjpg-streamer config. Unfortunately, I didn't make a note of it but it is a known issue with the pi2 and the USB camera output mode.

In the end, it really isn't worth using a Pi2 on this. The PiB is more than enough to handle the modest demands. I have heard that people using Cura on the Pi to do slicing have seen significant performance improvements, but to be honest, slicing on the Pi never seemed useful to me. I'm always doing rotations and multi-piece repacking and the GUI on my Mac was preferred for this kind of activity.

So, in the end, I went back to a standard Pi model B and reinstalled from the octopi distribution.

YMMV, but I'd say, don't bother with a Pi2 for this purpose.