Well, Pit Lords and Crypt Lords couldn't work as classes in WoW. Both of those units derive abilities from what their race is, not because of their role or job in the game. A Goblin Tinker or Alchemist are just Goblins that happen to work in those jobs. Also its clear that other races are using technology as well.4. This isn't really a reason for anything. The Pit Lord was in Warcraft III as well. So was the Crypt Lord. You can't (and shouldn't) play those things in WoW.
This is a good point, but its all about implementation. Monks and Rogues for example are both melee classes that use energy and wear leather armor, but the two classes play entirely different from one another, and Monks fill niches that Rogues can never fill and vice versa. In the case of Tinkers, the same could apply because the lore of the class is so wide open and varied. In my thread, the class was trinity hybrid that used Mechs. Blizzard could go in a completely different direction and it would still fit.5. But you literally just used Hunters as an example. All a Tinker would be is literally a Hunter with engineer and steampunk flair.
Thanks for your comments.