I promised myself I wouldn’t get into this. People really seem to get divided over the issue and take it way more personally than I think they should. There have been several posts on both sides of the question that got debated endlessly, but I finally decided that I would throw my two cents in. No wall-o-text, no analogy; just a simple and logical answer.
High End Raiding
If you define “raid viability” as being able to participate in the current tier of PvE content (ICC 10 and 25, and now hard modes): BM hunters can not raid as well as other specs, assuming skill and gear are equal. BM hunters are unable to contribute as much as they could with another spec on a DPS check, which means that they are being carried by players who are willing to play their highest DPS spec. If the carriers are strong enough, this might mean you can see quite a lot of PvE content, however.
DPS is not the only factor in end game content, but all the other factors can be taken care of equally well by all specs, and there will come a point where your (read: everyone’s) DPS is the deciding factor. Festergut is currently this point for most groups.
If you really like BM, be prepared to see a upper limit on how far you will be able to progress. Either you won’t be able to find places in end game raids, or the raid that does accept your choice of spec will hit a wall past which they just can’t, as a group, go. These walls exist for all raids that aren’t farming the heroic Lich King 25, but if you are doing 30% less damage than you could as marks, you are contributing to the positioning of this wall.
PUGs and raid weeklies
If you define “raid viability” as being able to group up and clear any other level of PvE content, then yes. BM is raid viable. For easier instances like 5 mans or any weekly raid quests, the DPS requirements can be easily met by a BM hunter.
Also worth noting- if you are not running with a group of skilled players, a skilled BM hunter can run circles around them. If you are in a pick up group for the weekly, don’t take any “lolBM” from losers who can’t beat you on the charts. The weakest hunter spec played by a good hunter is head and shoulders better than the strongest DK spec played by a drooling faceroller.
Additionally, it’s only a matter of time until everyone, including BM hunters and the drooling facerollers, will be able to contribute the minimum DPS needed to clear ICC. Gear is dead easy to get, and Blizzard will be turning on aspect of easy mode in ICC shortly. After that, all it will take to kill the Lich King will be the ability to stay out of the fire.