Who are the voice actors for the player characters and followers?

Solution 1:

It just so happens that all of the main cast is listed under the Credits button. I've written them down below for reference, including a link to their IMDB page where available. The vast majority of them have voice acted for other big games, including Star Wars: The Old Republic and Mass Effect 3.

Player Characters

• Barbarian - Female: Athena Karkanis
• Barbarian - Male: Dorian Harewood
• Demon Hunter - Female: Anna Graves
• Demon Hunter - Male: Robin Atkin-Downes
• Monk - Female: Rajia Baroudi
• Monk - Male: Jamieson Price
• Witch Doctor - Female: Erica Luttrell
• Witch Doctor - Male: Carl Lumbly
• Wizard - Female: Grey Delisle
• Wizard - Male: Crispin Freeman

Leading Cast

• Adria: Alyson Reed
• Deckard Cain: Michael Gough
• Leah: Jennifer Hale
• Tyrael: Jonathan Adams

Followers

• Enchantress: Sumalee Montano
• Scoundrel: Troy Baker
• Templar: Dominic Keating
• Blacksmith: Simon Templeman
• Jeweler: James Hong
• Mystic: Gaille Heidemann

Additional Characters

• Abd al-Hazir: Brian George
• Ashera: Courtenay Taylor
• Auriel: Cree Summer
• Azmodan: David Sobolov
• Belial: Jim Ward
• Captain Hale: Lloyd Sherr
• Captain Rumford: Greg Ellis
• Emperor Hakan: Sofia Pirri
• Imperius: Rick Wasserman
• Ithereal: James Horan
• King Leoric / Skeleton King: Joe J. Thomas
• Maghda: Susanne Blakeslee
• Mistress of Pain: Claudia Black
• Zoltun Kulle: Steve Blum

Furthermore, there are a ton of people credited for "Additional Voices" and "Monster Voice Effects".

EDIT: In the interest of providing a source for this, I've added a screenshot of the first part of the credits as well.