So now I have a question. Using that example, if difficulty 2 is nowhere close to what's needed to solve a block, that means that all work submitted while on a low difficulty is just worthless? This is something that I've been trying to understand for a while but haven't really found much concrete info about.
Define "worth".
It is "worthless" as far as actually solving a block goes. But the pool files it away and says "yup silverthornne has been doing work". Then when someone submits a share that does solve a block, instead of them getting the whole kit-and-kaboodle, it gets split between all those who submitted "good enough" shares.