What Aesteval said, their incompetence at not being able to do it by now though is a bit much... The average players shouldn't even know datacenters exist typically if things are being done right. This is usually the default in any other MMORPG with cross server. The average person probably doesn't even know WoW has multiple datacenters since you never even see them.
But yeah, EX content can't be queued using duty finder it's just a bad idea and hardly ever works.