WotLK's dungeon finder was originally server only. Then restricted to battlegroup(FFXIV is limited to datacenter).

The faction thing made some servers impossible to do dungeons that weren't max level on. Cho'gall for example, had less than 100 people on alliance side during prime time sometimes. That's why they added it.

Raiding was server only until Mists of Pandaria, outside LFR, and that was added late in Cataclysm... Which sucked then.

They're blurring the lines between realms more and more with connected realms and now Mythic raiding, last bastion of server community, is gone cross realm with 6.2.3.