These missions really need to be examined, my friend and I were doing diplo missions and the Reward to Cost ratio is really out of whack. Spending over 6k or more for only 10 DXP is horribly broken. They should at least give 20 dxp while higher level diplo missions (like first contact) give 30+
The Diplo DOFF missions are horribly broken which makes leveling using them impossible. waiting 3 real life days for 8 dxp is broken, so all thats left star cluster diplo missions to level.