Class quests are awesome. Yet, Blizzard doesn't seem to like them much. Well boo to them!
They claim that they are of limited value since only one class sees them. Yet having parallel leveling zones, unless you're looping back, you won't see them all in one go. They're for other characters and give crucial replay value.
I like class quests. They help make classes more distinctive, giving some flavor, without being the 'flavor' which was so often implicated in poor class balance and design.