... Um, really? Class mechanics? Playstyle? Theme? Weapon use? Race options?
Honestly, how is that even a question?
I mean, that very question disqualifies your tinker class. I mean, if we look at Blizzard and how they steadily removed totems from the shaman class indicates that they don't like turret-based gameplay, so by that logic the tinker can't have that playstyle, so, by your own question: "what makes them different than any other class in the game?"