Ok since I'm recently reading pretty much shit about Arenas in new Threads which are supposed to be approved but in fact didn't even working with the current Arena Matchmaking system, I'll try to sum up a bit.
The first point is that the 2.4.2 Patchnotes are wrong. The Matchmaking system doesn't look at the average rating of a Team, only the PR of the Person who is signing up is counted.
With that knowledge you can do some nice tricks, so you can switch your enemys by switching the groupleader, also its possible to play against very low or highrated teams.
One more thing is that I really often hear things like this "you win 1 or 2 but you can also lose 23!"
ok ... its very very simple. First: You CAN also win 0 points, but on the other side you lose 32 if you are losing.
You win 0 Points if you are facing a Team which is about 400 points below your Rating. So it is like this:
win: 0 lose: 32 ~ 400 rating differential
win: 1 lose: 31 ~ 375 rating differential
win: 2 lose: 30 ~ 350 rating differential
win: 3 lose: 29 ~ 325 rating differential
win: 4 lose: 28 ~ 300 rating differential
win: 5 lose: 27 ~ 275 rating differential
win: 6 lose: 26 ~ 250 rating differential
win: 7 lose: 25 ~ 225 rating differential
win: 8 lose: 24 ~ 200 rating differential
win: 9 lose: 23 ~ 175 rating differential
win: 10 lose: 22 ~ 150 rating differential
win: 11 lose: 21 ~ 125 rating differential
win: 12 lose: 20 ~ 100 rating differential
win: 13 lose: 19 ~ 75 rating differential
win: 14 lose: 18 ~ 50 rating differential
win: 15 lose: 17 ~ 25 rating differential
win: 16 lose: 16 ~ 0 rating differential
win: 17 lose: 15 ~ 25 rating differential
win: 18 lose: 14 ~ 50 rating differential
and so on ...
Question: I just wom a Game and got 16 points, but the second match I lost 18 points. Your chart cant be right.
Answer: Lets say your initial Ratings was like this: X: 2250 Y: 2274 (differential = 24 -> 16 points win / lose) , now Team Y wins = X: 2234 Y: 2290 (differential = 54) So its correct that Y loses 18 points.
And the last thing I hear very often: "You cant match the same Team more than 2/3/4/5/6 times"
FAIL! You can match the same team the whole day.
Anyway all that new "exploits" which describe how you can farm low teams to push your highrated Team just aren't working since you hit 1900 Rating and even before its not working because on a 1800 Rating you lose 28 points and only gain 4 .... so you have to win 7 games to balance one loss, be sure that you will match more often against S3 anticombo Team rerollers.
With all that Knowledge you can anyway do some nice and tricky things to push your ratings ... just think yourself.
Sry for (maybe) bad english. I hope this can help, I would post it to the guide forums but since it refers to the new exploit threads I think its better here.