Stick to other two specs and you will get invited.
From my experience in pugs you shouldn't have a problem getting invited most people will invite you, especially if you are bis everyone will prefer you over a second fury warrior that is missing smourn since as blood you will do more dmg in cases like that and you won't always find a second warrior who's BiS. But obviously a BiS char will do more dmg then a char that isn't BiS (with equal skill that is like always).

But when it comes to guilds it depends on the guild, like if you are in a progressing guild that is trying to do LoD but is not doing so well at it, then you are going to have a hard time. From personal experience I can say I was called useless like a lot, so I tried to prove them wrong I started doing a lot more research on the spec practicing different rotations on dummies improving my gear calculating gear etc. At the end I would be top Dps on most of the bosses (I was 6.4 at that time don't get me wrong it wasn't the spec it was the skill and gear that got me above them in dps you definitely don't want to play blood without smourn at least, don't do what I did), but some officers still called me useless even tho I would do more dps than the warriors. But then I was on 35 sfs and an officer decided to say "I'm starting smourn quest for my unh dk that is doing same dps as the tank, F you, you are useless" then he took shards for himself, and I was in this guild a really long time before this. I left the guild with all my chars, since then I didn't join any guilds and got all my BiS items through pugs and selling gold for coins on trade. So yea I doubt anyone has a worse guild experience then me here. That is mostly the reason why I'm not only trying to prove to everyone that blood is useful but also to myself... That is actually the only reason I don't prefer anyone to respec to blood who asks me, becouse I don't want anyone to get the same amount of hate that I did.

But sad background story aside, in guilds that farm multiple LoD runs weekly without problem you shouldn't have any problem what so ever except if they do 0% raid buff you probably won't get invited on that but that isn't that important at least not to me.

But also as this angry dude said you are probably better of staying frost or unh unless you really love the spec like I do.