There are now three ratings associated with PvP: Team Rating, Personal Rating, and Matchmaker Rating.
Team Rating
- Visible.
- Required for rewards.
- Reset when a new team is created or at the beginning of a new season.
- Not used for matchmaking.
- Primarily represents the team's standing relative to other teams.
- Moves towards the Matchmaker Rating over time. The larger the discrepancy, the faster the Team Rating will move.
- Looks like a new team will start with a rating of 0 from now on, rather than starting at 1500. This makes Arena less depressing for a below-average team, and allows Blizzard to stratify gear even in the below-average zone. For example, if a piece of gear requires 1300 rating, a low-ranked team can work to achieve that rating, rather than simply restarting the team or playing very few games in order to minimize rating loss.
Personal Rating
- Visible.
- Required for rewards.
- Reset at the beginning of a new season.
- Not used for matchmaking.
- Is primarily a control on Team Rating, trying to prevent players from leeching off a high-ranked team.
Matchmaker Rating
- Hidden.
- Not required for rewards.
- Does not reset.
- Used to match teams against each other.
- Looks to use a system like Microsoft's Trueskill to rapidly determine your true rating.
A lot of the confusion with the new system occurs because the Matchmaker Rating is hidden, but determines the change in the visible Team Rating. Essentially, MMR is used to match teams, and the result of the match changes your MMR depending on what your opponent's MMR was. Then your Team Rating changes to be closer to your MMR. A visible Matchmaker Rating would allow people to understand the system faster.
It looks like a pretty good system in general, if it works as advertised. The Team Rating is important, because Arena is a team sport, and it is important to be able to compare teams against each other.
One change that I think Blizzard could make is to ditch Personal Rating, and simply replace it with the Matchmaker Rating. This would make the Matchmaker Rating visible and required for gear. The Matchmaker Rating can also serve the same control function, preventing low ranked players from just joining high-ranked teams for gear. This would simplify the system and make it more transparent.
Edit: Any comments about "gear > class > skill" or whatever will be deleted. That argument is uninteresting and irrelevant to this post.