It will give +2 total damage and to-hit across the board, regardless of weapon. Here's why you don't count it. You can't always depend on having a bard in party, and if he buffs you, he can also buff the barb. You could chug a pot, but so could the barb, ect., ect.
So you are back at square one.
The same goes for any other group buff.
Dude, I'm tired of this argument. You haven't proved your point to anyone with half a brain cell. You have an impressive DPS build. That would've gathered you respect here. Then you ruined it by making a half-assed claim that's it will out-damage anything in the melee game, and have argued it in the face of all logic to the contrary. You've lost the respect of anyone here with a working knowledge of the game. You cannot match a barb's DPS with that build.
Every counter you've offered has been picked apart. The original damage numbers you posted in your *proof*, had the barb using additions that he can depend on every swing. By comparison, you gave yourself modifiers that are situational, and cannot be relied upon. Then you don't wanna bring crits into the equation, when the barbarian will have the same crit range with a greataxe ( that's right, sans raid loot that you are depending on ), but is doing a hell of alot more damage than your build.
In closing; Impressive build. Impressive DPS. But it is not what it is billed to be.