So, the reason they should be tinkers is because you want them to be,despite having almost no lore behind it, and that the class is a little person club so no big boys allowed, despite the lore showing Mag'Har and Dark Iron Dwarfs and Lightforged having a strong mechanical aptitude. Still makes no sense, sorry.
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Your ideas for the class make a lot more sense. Someone was throwing around Artificer as a name, which sounds a lot better than tinker, in my opinion.