I went through the armory and did some analysis. If you fight a 2000+ rating 5v5 team, you have a
96.0% chance to face a Warrior
93.4% chance to face a Paladin
76.3% chance to face a Priest
73.4% chance to face a Mage
39.6% chance to face a Shaman
38.5% chance to face a Rogue
35.7% chance to face a Hunter
25.7% chance to face a Druid
16.9% chance to face a Warlock