Just wanted to mention, EQtraders has Distillate of Immunization VII and VIII listed: these list Hearty Mushroom Spores and Robust Lizardman Blood as the drop components for level VII and VIII, which keeps with the clues the in-game books give: "spores from living fungus" and "blood from bipedal lizards", respectively.
A look at Lucy revealed Exceptional Zombie Essence; can you get a closer match to 'the essence of some of the deadliest zombies'?
At the same level, the curing potions list "blood from what he said were talking rats" as the drop component and, lo and behold, I see Exceptional Ratman Blood on Lucy
This is what I theorize: For VII, VIII, and IX levels, the Distillates require a Hearty, Robust, and Exceptional type of drop, but they will not necessarily be of the same type.
Lucy lists the following items: Hearty Goblin Blood, Hearty Mushroom Spores, Hearty Shissar Blood, Robust Shadow Essence, Robust Lizardman Blood, Exceptional Shissar Blood, Exceptional Ratman Blood, Exceptional Zombie Essence, Exceptional Shade Essence.
We'll assume that each drop ingredient is used in only one kind of potion recipie. VII and VIII Elixirs/Effusions use Hearty Goblin Blood. VII curing Distillates use Hearty Mushroom Spores, and the non-curing Distillates use Hearty Shissar Blood. Of the Robust ingredients, Robust Lizardman is used for level VIII curing Distillates. The Elixirs/Effusions don't need one of the drops since they use Hearty Goblin Blood still. At level IX, we find very strong clues pointing pretty much right at Exceptional Zombie Essence and Exceptional Ratman Blood for the Elixirs/Effusions and curing Distillates, respectively.
This leaves us three items; Robust Shadow Essence, Exceptional Shissar Blood, and Exceptional Shade Essence.
I'm willing to bet money that if you drop a Robust Shadow Essence, Valerian Root and Fine Potion Vial in with the proper size ingredients for Comprehension, Skinspines, or Regeneration, you come out with a level VIII Distillate, or a message that 'You lacked the skills to fashion the items together.'
As for the level IX Distillate ingredient, I learn towards the Exceptional Shissar Blood. Robust Shadow Essence is also used in Mist of the Wolf I, so if it is serving in a 'potency ingredient' role there, it's a logical conclusion that Exceptional Shissar Blood, present in the recipe for Mist of the Wolf II, would fill the same role.
These are my conclusions on the progression of drop ingredients:
Elixirs and Effusions: Hearty Goblin Blood for level VII and VIII; Exceptional Zombie Essence for IX
Curing Distillates: Hearty Mushroom Spores for Level VII, Robust Lizardman Blood for Level VIII, Exceptional Ratman Blood for IX
Non-Curing Distillates: Hearty Shissar Blood for level VII, Robust Shadow Essence for level VIII, and Exceptional Shissar Blood for IX
I would guess that Exceptional Shade Essence is the drop component for level III Tonics (per the Liquid Power book, the beta text of which is available on ), and that should wrap them all up.
Just wish I was going to have time tonight to log on, do some hunting, and test this myself =\