At the moment, the pve missions are up when you are low tiers, but more tier you get more expansives modules are but pve mission remain:
the same amount of credits
more level you grind and more the missions are so easy and not attractive at all. In T4 the mission are boring, there is no challenge.
loots are not adapted, when you do a mission in T3, getting T2 loot is clearly not adapted.
Having different scenarios depending on levels.
For example rank:
* 1 - 3 should be able to do missions level 1 only
* 4 - 6 should be able to do missions level 1 and level 2
* 7 - 9 should be able to do missions level 1, 2 and 3
One level = one map = one mission
More the mission level is up more the difficult is harder, more credits, loot in adequation to the level (Tier 1 for level1, Tier 2 for level 2 etc…)