I realized that this should have been included in my 1st post, but I missed adding it. Disenchanting has bonus ranges depending on the tier of dust.
0-250 Seeds of Terra
251-500 Drops Riva
501-750 Shades of Nox
751-1000 Cinders of Pyron
Essentially, if you have lvl 250 d/e'ing, you have a high % to get bonus Seeds of Terra. 500 and you have a high chance at bonus Drops of Riva, etc. Personally, I've not worried about the bonus and d/e'd everything to lvl as fast as possible.