Join as group

Forgive me if this is common knowledge, but I cannot for the life of me figure out what is wrong.

I have a group of 4 shammies, but even when I join a battleground as "Join as group"
I still get disbanded and my team members reassigned to random groups.

What am I missing here?
Do I need a full 5 man team?

They have changed things over time. The way to look at it as it stands now, is join as a group just queues all your players at the same time. Good to get them to pop into the same BG, but that is all it helps. The accept BG part is what puts you in the same group. It doesn't guarantee that it happens, it just tries. But since no twinks, crazy number of people are doing BG's, so crazy number of people are joining. You probably won't have any luck getting in the same group, sorry. Used to be largest group was leader, that is gone. Used to be you could move people around, so you could just get promoted and move yourself, no more. Just have to hate it and move on.

Ah! that certainly explains it then, thank you very much.

Guess some rewriting of my macros are in order now then :)
(No assist party1)

Yeah, since I have started doing WG and AV I had to go back to /assist focus.