Heaven forbid you're not FATE farming or killing 4-5 of the same mobs for quests or hunting logs.

Either way, it is true certain mobs have way too few spawning locations. For the level 45 Alchemist quest you need a material called Pudding Flesh, and this item can so far (to my knowledge) be found on a Pudding encountered in a levequest. That's it. No other mobs in the game drop it (to my knowledge, again).