Breja: To be fair, it's not exactly a new thing, nor a bad one by definition. There's plenty of examples of such tropes being re-examined, subverted or parodied. Doing so is one the pillars of Discworld, which went from being a parody of other fantasy (including very much the classic D&D) to being one of the most popular and beloved fantasy settings in its own right. It's all about how it's done, where an why. Pratchett was a master storyteller and a wise man with tremendous insight and uncompromising vision. This on the other hand is a knee-jerk reaction of company willing to break their flagship product for the sake of a note from the PR department.
Sure, as babark mentions above Warcraft successfully changed the orcs background, very successfully in fact. WC3 remains my favorite rts to this day, in large part because of its story and atmosphere. WoW even somewhat managed to do the same with the undead, or at least a faction of the undead.
So no arguments there. Truthfully I was and am more concerned for the Tolkien and Warhammer universes, where the evil races are afaik(?) pretty irredeemably evil and/or monotone in other ways - like all-male astartes which bothers some people.
Rather inexcusably I'll admit, I've only read one of Pratchett's books :\