The other problem is that at my fp (and probably mj), we can't find many encounters or interactive encounters. So hidden interactives seem to be our best bet to do encounters. However, they are much lower than the hidden interactives. eg. A normal pirate party interactive is 162 tril fp but a hidden one is only 42 tril fp.
I aggre there to low to be worthwhile they power seems close to what some of the smaller aliens are. However the plus side with aleins is there are tons of them and they take less turns then interactives. However hidden interactive take 10 turns just to get to the first step 5 to go there and another 5 to start the missions. After that you need to spend 20 to 50 turns on average to complete it. So the turn cost vs reward is too low for it to be worthwhile to do em.