I've played over 200 games with a 52% win ratio, yet I'm ranked at 1650. I've armoried several people who play on the US servers and they somehow manage to get 2k+ rating with fewer games played and a lower win ratio... and this is on the harder battlegroups like Bloodlust.
Does it depend on the number of teams in your battlegroup? There aren't that many teams in mine (once went 3-7 in 5v5 for points, managed to get ranked 200 something for that week) so I'm guessing that might have something to do with it. But I looked at the wowwiki page on Arenas and the formula for rating calculation seems to have nothing to do with the number of teams....
How does it work? It's annoying to think that someone can get arena gear so much faster despite losing proportionally more games :/
When a Arena is over it will tell you what your matchmaking rating is. This is what your team is queuing at. Since you have to work from 0, it helps you get to that number by making you lose next to nothing and winning a ton up until that number. This number changes as you interact with other teams but eventually you will get there.
Those teams that you looked at probably had a matchmaking rating of 2k+ (acquired last season) so the system will queue them against 2k players. If they can keep their matchmaking rating up, it's simply doing enough games and the system will take you to the level that you play at.
It depends on what teams you are winning against. If you keep loosing to the teams with a higher mmr you will not rise. Win/lose ratio does not mean as much with this system, its all about beating the right teams.
The change in the new system is that you will fight teams around your supposed skill level i.e. 2.7k rated teams wont have to farm 1k rated teams if they decide to level a new team.
Yep - it's all about your hidden rating. I would like a better explanation of how it works. After the change to the 3s/5s MMR that was intended to make it easier to hit 2350 in 3s/5s I played some 3s in an already established team. For some reason our MMR was showing in the 1600s even though our team rating as in the 1800s. Our healer left after that week then this week we do some 3s with a new healer who hasn't done 3s at all this season. Suddenly our MMR is 2000 (team still in 1800s). So even though we have a 50% win ratio we quickly gain 100 points in just a few matches. I swear it just feels easier playing with higher MMR - maybe because you're less likely to face PvE geared burst teams.
I think one of the issues with MMR (which is also one of its key strengths... double edged swords are fun) is that its more than just the number we see... its a full calculation including a confidence factor. We don't see the confidence numbers so I can't help but think some of our understanding is limited when we see weird output like what you just described.
Your original team may have had a high confidence factor that you were lower rated. Then you got a new member, the confidence number slacked off a bit since it 'wasn't sure' so it opened up for a slightly better priest (probably anyway considering the 2k rating compared to 1800 rating... regardless of the MMR of 1600) to move your MMR higher quickly.