In Isle of Quel'danas mobs spawned instantly at times if enough players were around. Crzs are only counting players from their own server. There could be 10 players waiting for mobs to spawn and the zone's server is still reading 0 players in the area.
You're right about nodes/herbs in Quel'danas being rare, but we also had 4 other less filled zones to farm in. With CRZ every zone is Quel'danas, but mobs, pets, rare spawns, nodes and herbs are spawning really slow. When I need low lvl ore I have to check the AH, then hope my server's bot got lucky and was able to farm the ore I need.
I doubt Blizzard intended this, but they appear happy with CRZ and it's bugs. As long as people keep saying, "pvp on a pvp server; deal with it" Blizzard will keep CRZ, while ignoring the many negatives CRZ brings that have nothing to do with Pvp. If CRZ worked as well as Quel'danas did in BC, people wouldn't be complaining like they are now.