>This one would be especially interesting to see completion vs playtime.

agreed. This is one of those situations where the game is so massive there might just be a lot of people who get caught up doing whatever they feel like doing and never really progress the main story forward. I know that I'm that way with Skyrim. I've never once completed the story for Skyrim on any platform, ever, but I've sunk about 100 hours into it on Steam.