Some of the reagents aren't found in the starter zones, such as Namira's Rot for example.@Fexelea All 18 reagents are in all zones. Some spawn in specific topographical areas, like nirnroot and water hyacinth spawn near water. Solvents tend to be area based, but they have a great deal of overlap.
Working on updating this guide. Anything anyone wants in particular? Got the table updated and working on pictures and such over the next few weeks.