Where do you get schematics for the tanking item modifications, such as Guardian, Force Wielder, and Patron? The Trainers do not seem to carry these schematics and no one I have asked has any idea. Can crafters even make these modifications? (By modification, I mean any and all- Mods, Armoring, etc)

If it's anything like Artifice, you get absolutely showered with every type in the game at 50 when you hit 400 skill. Before that, the only way I can think of would be reverse-engineering quest rewards.