I added a discussion page on the nightmare lockbox for drop rates. When enough people add enough data then more precise estimates for drop rates can be given. http://neverwinter.gamepedia.com/Talk:Nightmare_Lockbox#Drops
The Foundry is basically the only thing that makes this game stand out from any other and the only reason why many people were attracted to the game. The Foundry is a make it or break it for Neverwinter not just a feature. If this keeps up or the Foundry becomes unreasonably annoying to use, there are plenty of other games…