Dragon Sigil Farming

Some of you may already know this, but I was irritated at not being able to find any info on the dragon sigil farm route. So I ran it for a few days and here is what I determined. 

Pickup the quest in protectors enclave and run the solo dungeon (ghost stories or miner tunnels), this is 1 sigil. Then head to Rothe Valley, that place will get you 2 more. After that, whispering caverns will net you 2 more.