Hi Adotlin. These days Warcraft has besides Guilds also so-called Communities. These are groups of players cross-server and cross-guilds, for example to do dungeons or raids. I don’t know if you also play Alliance, because then communities like (Alliance) Scared of Dungeons EU EN or [H] Mythics - Calm Keystones are good places to team up. And for Horde there are similar communities, but of those I do not have links handy 
And you can be member of multiple communities!