The ranking system is not confusing at all. It's based off your average round of the games on your player channel vs total downs off those games. The way it was setup in BO1 without rank was fine though I still like the expanded stats in BO2 as piece of mind.
You don't haven't to play day in and day out to rank up. When jimmy tweeted that " rank is alive" he meant its based on your activity ( games shown on player channel) and how well you do in those games. Example:
Say you play 5 games getting to rounds 20,25,30,35,40. Add those
and u get 150 . Divide that by the number of games played (5) and u have an average round of 30. That average gets pitted against the total downs of those 5 games. The higher your average round and lower your total downs are the faster you will rank up.
The ranking is not decided based on only your player channel games. Plenty of people have ranked up in custom games. You're right about the way it works though. It's just based on all your games played. It's much easier to track though if you play public.
Custom games appear in your player channel. If u don't play and clear out your channel you are resetting the process for you to rank up. So what I mean is if you have a bad string of games played ( custom, solo, and public continute towards ranking up) and you have an average round of 15 it's better to not play for a while and let your channel clear it's self out rather than playing more games with that current average " 15" and spending more time trying to bring up a low number.
That is boosting and awful thinking . You will not rank up doing that if you start the game on 20 only to end it right away . At most you might move up from bones to skull. Trying for the knife and shotties actually require you to get to higher rounds consistently.