According to a recent post by Ghostcrawler there are three primary reasons that they killed off the 2v2 arena bracket this season.
First, the most successful compositions were dominated by classes that were "well-rounded... with lots of offense and defense..." Think Paladins and Druids. Ever try to kill a good Resto druid one-on-one? It can get a little bit insane. Same thing happens in the twos bracket.
Secondly, there exists a problem with healer balance. Consider the following scenario:
- A healer can't keep himself and his partner up in 2s, therefore the healer would never be successful in 3s
- A healer can keep himself and his two partners up in 3s, therefore would be over powered in 2s