The problem here is that missions granting cores are always "the best". Would you care as much if those incorporate missions just gave you back the stab hit you took doing so, or some other reward not related to cores? Unequal rewards are the issue with the current mission set-up much moreso than any other flaw. Not surprising since many missions give the same rewards as they did in EU 3 while others have been updated over the years to give better rewards. For example: the manufactory missions weren't so terrible when that 4 star leader was fairly uncommon but with easy 5/6 star due to cultural tradition it's another story.