It appears that the version of Deathwing spawned is the current one that flies around Azeroth and burns zones to the ground, killing all NPCs, mobs, and players. We can even see the player in the video get the Achievement "Stood in the Fire." There is no indication this is the version of Deathwing that will spawn in the raids. We didn't see any players on his back, which is something we know will be possible during the fight.
We believe the video and reports are credible. And while it happened on the PTR, there is little possibility of this happening on the live realms. "Fly around and randomly destroy zones" Deathwing doesn't hit the cities, and GMs rarely, if ever, make themselves known on the live realms. However on the PTR, as the video above shows, things are completely different.
Thanks to WoWCynwise and NDMiko for the Twitter tip and video.
Brace yourselves for what could be some of most exciting updates to the game recently with patch 4.3. Review the official patch notes, and then dig into what's ahead: new item storage options, cross-realm raiding, cosmetic armor skinning and your chance to battle the mighty Deathwing -- from astride his back!