I have been trying to figure out a situation were the +15 points on a Spotter is worth while.
I noticed in the TAO/Spotting Laser discussion for the GrimDark that it effects a full unit that is targeting the spotted unit, which means it is adding a +1 to multiple attacks or the attacks from a larger unit. However in firefire, the same effect is only impacting 1 other unit.
Given the point range I did a quick crunch of a Spotter + Spotting Laser [35 points] + a Stealth Suit [35 points] vs. 2 Stealth suits:
No Spotting laser hitting on
As you can see, for the points, it is better to just get 2 stealth suits over the spotter + suit. I obviously don't want to take the time to analyze every possible combination, however I am fairly confident that it is balanced better toward the non-firefight unit compositions then the Firefight compositions.
I don't have access to the points system, but I do believe this is one of many abilities that don't just transfer over cleanly from GF to GF:F (I have ran across a few others that the points don't seem to work well in GF:F but might be fine for GF).
Unfortunately not all special rules work well for both games with the given point costs, but we'd like to avoid tinkering with them between the two systems because that tends to lead to more confusion. What we usually do is adapt the special rule in question so that it makes sense.
In the case of the spotting laser I see that it needs some tweaking however. Maybe we can change it so that once you remove the marker all models get +1 to hit until the end of the round. That way multiple models benefit from the same marker and the spotting laser's cost is a bit more bearable.