Recently I turned DM audio back on while playing the new quests. I've left it on, and here are my impressions:
I understand why he's in the game, but man his voice is annoying. It doesn't sound like he's invested in the quest at all, and he's just reading boxed text someone else wrote.
Same as above, but less annoying.
6: Kiwi man DM
I don't remember anything about this guy.
5: Orchard woman DM
She sounds like an ordinary person talking to you. This would be sufficient for a home game, but not exceptional.
4: Default man DM
This guy does a decent job, especially seeing as how he voices SO MANY QUESTS! He has some skills at voicing, but occasionally really screws up (cry for help, coal chamber).
3: Droaam woman DM
The newest hire, she sounds like your grandmother telling you a bedtime story - if your grandmother was Julie Andrews. Good narration, but never punched up.
2: Korthos man DM
Some people have complained that he gets TOO emotional about mundane stories. I say there are no mundane stories in Dungeons & Dragons.
1: Carnival/Madness man DM
My favorite. The only downside, if it is a downside, is he sounds like a professional voice actor, not one of your friends running a home game.
Droaam woman and Madness man get an unfair advantage because they use other people to do the NPC voices - something Default Man could only afford once. Perhaps WB has provided more funding or larger talent pool for voice acting, or simply encouraged Turbine to take it more seriously.