I didn't do a full ghost run of Deus Ex: Human Revolution because some of the people in that game really deserved killing. Even if I had, it wouldn't have been a proper, no deaths playthrough. The game's Pacifist achievement reveals the problem: "Complete Deus Ex: Human Revolution without anyone dying by your hand. (Boss fights do not count.)" Yes they do! It's still a murder!
For Deus Ex: Mankind Divided, things will be different. You'll be able to complete the entire game without killing a soul, even the bosses.
Here's executive game director Jean-François Dugas giving confirmation:
Human Revolution's Missing Link DLC already gave us a boss we could subdue rather than kill. That boss fight was created in-house by Eidos Montreal, rather than being outsourced like the battles in the game proper. Hopefully, Mankind Divided will get the same sort of treatment by the game's primary developers.
For more on Deus Ex, check out Tom's detailed trailer analysis.