never heard of farming green shards in NM before nor do I plan too but curious as to whether there is a confirmed efficency to do so? Also, just glad "Wow Really" wasn't referring to Classic arena being too difficult :)
You can't get Mystery Shards from NM Campaign. I think it's indicated on the left side when you select a campaign under "Misc. Drops". You'll find that mystery shards are taken out of the possible drops.