There is a very detailed writeup on using scouts to rank up in the link below, but the key point is that the scouts are now worth somewhere between a dangerous and deadly pilot.
"Basically as Deadly rank, you get 1.25 progression points for killing an Elite ship, 1.00 for killing a Deadly ship, 0.75 for Dangerous, 0.50 for Master, and 0.25 for Expert."
"When you’re at Deadly rank they [Thargoid scouts] appear to have a multiplier of 0.833333, which is above a Dangerous kill, but below a Deadly kill."
I was out fighting Thargoid scouts in threat level 4 Non-Human Signal Sources in Asterope when I received the message in game that I had reached combat level Deadly. I killed the last two scouts in the group and knew I was now embarking on the dreaded combat grind from Deadly to Elite. That’s...
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One advantage with scouts is that using gimballed AX multicannons they are really easy to kill, and as
@Kira Goto said invasions are great fun as long as you can find one.