Just to reiterate the OP's argument. This thread is not about "Leves give too much SP." It's about the fact that you get the same amount of SP for doing an easy leve, just because it's fast, as you would for doing a challenging leve. The reward is the same for taking it easy as it is for taking on a challenge.

Right now the mechanic seems to only function on 2 variables: Completion speed, and difficulty setting. What this equation is missing is a variable based on the difference in player level and levequest difficulty, just as there is SP variable based on the difference in player rank versus mob rank.