I was thinking about this. How bout instead of having to lvl once you finish a color of a daily it unlocks a new one.
The unlock able ones are x3 the awards maybe as the normal ones. This will be one of the dailies already in that section but be x2 the difficulty. For the highend instead of that what if its an ascended. Brighter gray has a 1/100 chance for a random ascended,brighter purple has a 1/35 chance for a random ascended, and the brighter green will have 1/2 chance for an ascended (the green ones are pretty hard so it should give out a nice reward)
i.e. if you finish all the purple colored ones itll unlock a brighter purple one and that one gives 15k ic and times 3 the amount of xp it usually gives.