Indeed, it is very hard right now to farm a decent amount of Corrupted souls to run an entire day of raid rifting.

Here are my suggestions in relation to that matter:
  1. Corrupted and Malformed souls can be bought using Plagues of Achievement
  2. Create a specific vendor that allows you to buy 1 Corrupted Souls for 2 Malformed Souls
  3. Raid bosses should have an additional drop of 2 Corrupted souls per kill, or even better, 5!

And in regards to the Crafting Plagues, why not have the Crafting vendor sell them for say, a set price of 500 Artisans mark? Some of us have been doing dailies for so long and have yet to have a crafting plague. Would be nice for those unlucky ones.