I think the developers should look at the numbers in terms of average time played and adjust the drop rates accordingly. If it takes two or three times as long to play through ground missions then the drop rate should be two or three times higher.
Now, I have played a number of the new STF missions (mostly space) and the drop rate does not seem unreasonable for items that are supposed to be very difficult to obtain, but if you want a proper balance between space and ground you are going to need to account for the fact that the optional ground missions are much more difficult to complete and the time it takes to run them is much longer. There also seem to be more dropouts on ground missions, either because the longer investment of time means that people are more likely to need to leave or because of "rage quitting".
Both the space missions and the ground missions are fun, but the rewards should be more commensurate. Look at the data and make some adjustments please.