Mk4 scouts mean very little to me ...
I assumed that mk4's would be some sort of ultimate cloaker that would balance its 'cant see me, cant shoot me' with a very low speed.
It sure didn't work out that way for me
They die at like the thirth gate they go through, roughly as far as you can get a transport before it blows up when entering the planet.
At a higher cost(iirc), 30mk3 scouts will get some info from the other side of the map, and you wont have to wait for 10min for the info you really want to come in.
I may be very wrong about the mk4 and just used them poorly, but at the moment they seem fairly useless to me.
(If not for the balance than for the fact that often by the time I do get a mk4 fab I already scouted 70+ of the 80 planets.)