You whisper each person on the list and you form a pool to create your group from plus the added adventure of making your way to the summoning stone with a group of your server comrades. WoW dungeons were a lot more fulfilling back then
Or you wait, potentially spamming the LFD channel in Orgrimmar for 2 hours, get only 1 person to join your BRD group and then quit, having wasted 2 hours because not enough people were sitting in Orgrimmar.
That was an actual experience of mine back in Vanilla.
But you know which one was better. doing BGs with a guild-member, then oh hey, the guild-member is going to a MC Raid, oh hey, they need people!
Oh hey, I'm an enhancement shaman with no resto-spec. Too bad for me.