Originally Posted by
Darsithis
I know of no dungeons they've ever removed, and they've only removed three raids from the game, all of which were brought back as raids or dungeons later.
What pets or mounts were removed?
Challenge modes aren't removed, but the earlier ones are closed simply because it makes no sense to have a timed dungeon based on current gear, stats, and abilities usable by people 10, 20, 30 levels higher with new abilities that can prove dungeon-breaking.
As for the rest of it, well, every game changes. SWTOR overhauled its talent system, for instance.