will try to answer the crafting questions as best I can
The exotic materials (ie. synthetic matrixes and molecular stabilizers etc.) only dropped at the end of ops. I am not sure if they still do or not. I haven't played a story mode Karaggas or Exsplosive Conflict or Eternity Vault in some time. I do know in hard mode I don't think they drop anymore. You can also get them in cartel packs from time getting 5 or 10 at a time. Other than those 2 places the gtn is about the only place.
As far as reversve engineering items to get purples you can go from green to purple on all items up to level 49 if you don't have the exspansion. The dread guard you have to re the purple to get the schematic as well as the classic gear and the old rakata gear you can buy from the makeb vendor with planetary comms.
I this helps and I hope I am right on this.
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