Dean Ayala responded to a thread on Twitter about matchmaking in Arena and was able to confirm some details on how the system works. 

  • Your record with your deck is assigned a value.
  • The matchmaker attempts to match you with another deck with the same value, but possibly a different record.
  • If a match can't be found after some time, it will slowly expand the search range until one is found.
  • They have enough data to determine how different records do against each other.

Dean also went on to confirm an internal skill rating for players, though it isn't used in matchmaking.

  • They track a skill rating for players but only use it for data tracking.
  • Match outcomes are decided almost entirely by the skill level of the players involved. A fact they know due to the skill rating metric.

You can read on below for his full tweets.

Quote From Dean Ayala

All records (0-2 –> 11-0) are assigned a value and are then matchmade by that value. This isn't exactly correct, but it looks something like this:
0-2 = -10
1-2 = -9
0-1 = -8
etc
etc

The order of records and distance between records is some complex table. Basically we have enough data at this point to understand how well a 2-0 performs vs a 2-1 or an 8-2 performs vs a 0-0 on average.

And just like other matchmade modes, the matchmaker looks for an opponent with an identical value, then after X time extends the search parameters a small amount and repeats that process until a match is found.

Contrary to popular belief, match outcomes are decided almost entirely by the skill level of the players involved. We know this because we track a skill rating as well we just don't use it for anything outside of data tracking.