I can tell you where I got mine from (of course, you will need to kill them over and over again until you get what you need but they exist):
T4 armorer (2 spots):
T4 blacksmith (3 spots):
^^ this one is also good for damage carpenters.
I can confirm that the above spots spawn all 3 types of T4 armorers and T4 blacksmiths but it took me about 200 kills of each camp (on 2 servers) to get a full set of T4 armorers/blacksmiths. I was after a bladesmith and shieldwright but got the rest while trying to get what I was looking for.
The bigger camps have also random thralls so you may get lucky there as well.
Happy hunting!
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Oh and one more for Blacksmith (Bladesmith or Tempersmith, no Edgesmith). This one is also good for alchemist and berserkers:
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I would recommend hunting in the new lands because you get fragments + statues in the process as well.