Armature: automatic weights not working correctly I've rigged a few models and automatic weights always worked pretty good, compared to what's happening to me now. Vertices assignment is all over the place and I don't know why. This happened only on 2.79 but it might be an accident. I know automatic-weights isn't perfect, but it used to work so much better in the past for me, way more accurately. Just asking whether maybe patch changed something, or did I mess some options?
Happend to my model as well, exactly as you described.
Weighting couldn't be solved on the model, so I removed entire head and then applied armature with automatic weighting. Weighting was solved as in the bottom image (some weight, though not visible, was all over model). Then I removed eyes, glued head back to the body and weighting was solved normally.
I had bones sticking out of mesh when got this wrong weighting.