Anybody can post anything onto a wiki, though. So that's hardly proof.
This is a case of one person thinking a guy sounds just like Michael Dorn (in this case, the Tauren NPCs), and then putting it on a page, and then EVERYBODY accepts that page as fact and spreads it like wildfire.
The voice is too high for Dorn, I think. His is lower than that.
"You're not smiling, Joker. I thought you found death amusing."

Yes, he is uncredited, however he really did provide some Tauren voices, as well as some of the Stormwind guards. I think he may have also done a few voices in other locations.
This is taken from Memory-Alpha:
Dorn's voice can be heard in many video games, as well. The2000se include Gabriel Knight: Sins of the Fathers, Fallout 2 (narrated by Ron Perlman and also featuring the voice of Dwight Schultz), Forgotten Realms: Baldur's Gate II - Shadows of Amn (with Alan Oppenheimer, James Horan, and David Warner), Emperor: Battle for Dune (with Michael Bell, Hamilton Camp, Kay E. Kuter, Vincent Schiavelli, Michael Bailey Smith, Musetta Vander, and Nicholas Worth), and the ever-popular World of Warcraft. More recently, he was heard as the voice of Maero in Saints Row 2, which also features the voice of Daniel Dae Kim, and as Gatatog Uvenk in Mass Effect 2 (with S.A. Templeman)

I'm pretty sure he's not in World of WarCraft.
He's not credited, and those NPCs don't sound all that much like him. Not enough that I'd ever be sure it's him.
"You're not smiling, Joker. I thought you found death amusing."

I knew it! I just got this game three weeks ago and that has been driving me crazy. I just remembered to check here today and saw that he does indeed do some voices on WoW. I haven't watched TNG in years, so I'm amazed I recognized his voice immediately on various NPC characters, but I did. I guess he has a very distinctive voice that you never forget it!

I'm glad to know I wasn't imagining things, and he DID do some of those Tauren voices.

This message has been deleted.

I'm pretty sure they used his voice for the following npcs.
I'll keep checking for more and update you.
Edit:
Redoing my whole post because I'm an overachiever.
Atepa
Thunder Bluff
Rumstag Proudstrider
Thunder Bluff
Tal
Thunder Bluff
Tharm
Sun Rock Retreat, Stonetalon Mountains
Poa'ka Swiftmountain in Thousand Needles
/moo

I swear he's the voice of the male guard in Stormwind. Some shopkeepers could also be him.

I've only been playing a few days but he seems to be lots of NPCs with short lines like "Can I help you?"
I like posting in forums about movies.