Dungeon and raid channel


I would like to know if the dungeons and raids are played on a channel in location we matchmade for them, or on a separate channel?

Why? Because I keep noticing that if one channel is full and I’m too lazy to switch to an emptier one, I have terrible fps drops and sometimes higher ping, and when I do, or even better, when I play from an island it’s much better?

LIke, knowing this would help me have some piece of mind when it comes to channel switching.

Keep in mind that even that takes a bit of time for my laptop.