Its not the Channel or the "Group" that is biased twords DH's, Its just anything a DH can DO* Anyone else can do much better and then some. Hunters are just pure DPS* they don't bring much else to the table. Barb's/WD/Monk's are great preppers (Some Wizards such as the Meteor Build) For FOM/CRYPT Elites should only take a matter of a minute to prep. I finish My Crypt/FOM prep and usualy help get the last elite Preped and Killed. And wizards Just out DPS 90% of DH's and tend to be more Mobile on Average.
* Some builds work for party but it sacrafices your dps and just like everyother game if you can't be the hero that does ALL the damage most people dont wanna do it (Carries in LoL, DPS in WoW, ETC ETC) Power to the Tanks/Supports of Games!