I think a big reason for the nightmare mode was because we asked for it
Indeed, as like Raze said in his post
Originally Posted by Raze
The 'hard' difficulty in DKS was no longer hard, so by popular demand another difficulty level was added, ...
It's a nice challenge !
On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin, it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !