WoW has never been a dark game. It's had dark moments, people die, and there are some very dark images, but its always been very colourful fantasy, not dark fantasy. In fact of all the games (before Overwatch came along), WoW was probably the more light hearted silly and fun game, I found Diablo and Starcraft more adult in tone.
I like warcraft being the tone it is. It's apart of it's charm, to take that away makes it not warcraft. Warcraft has always been the best part of a Saturday morning cartoon.
For starters that's rose tinted glasses, if you were over the age of 18 when Warcraft 3 came out like I was, you'd know Warcraft 3 was never 'dark' and that cinematic (while awesome), is cheesy, the dialogue is great but its very action movie one liner "What are you doing my son" , "Succeeding you father", that last quote sounds like something straight out of an Arnold Schwarzenegger action flick.
This delusion people have thinking Warcraft 3 was a great serious dark masterpiece is starting to annoy me. It's a great game don;t get me wrong, its one of my favourite games of all time, but I am not tied down to this crazy notion that the game was once some really dark and edgy game. It really isnt. lol