I think a tinker class would work in Warcraft. We have Goblins and Gnomes. The legion is big on building large robots, and we’ve seen a steampunk airship in an opening cut scene now. We also have a Tinker as a base representation of Warcraft in Heroes of the Storm. I know that what happens in HotS is not lore for the games they pull from, from the very beginning this character, a ticker, was included to represent Warcraft, and it is not out of place. It does seem like some crazy thing that isn’t from Warcraft. Gazlowe fits right in next to Arthas, Illidan, and Uther.
I used to think that the Engineering Profession would overlap to much, but I realize now that simply isn’t true. Inscription and Death Knight both use runes, but they do not overlap in game mechanics in anyway. The Engineering Profession has little to no combat abilities.
There is a lot of sentiment about their being too many classes in the game now. I totally get that. I personally think that tinker could be a forth spec for Rogues. The Defias Bandits have a strong leaning towards engineering. I think it would be a good way to add a tanking spec to that class. (literally, in a tank)