I think i used 2 dragon drones with 6 rogues. In the second wave, only 4 units can attack them, and because the drones can hit 3 units at once, even 5-6 units are definately enough for that. A bit lucky terrain needed and the enemy units' lucky move to be next to each other when attacking with the drones but absolutely doable with 2 drones, i made it with the first attempt. With lower boost it can be a bit harder... I used this combination more times against 8 eels and 8CRABs (7CRABs, 1 sub cruiser) in the 4th difficulty (and maybe by some other encounters too), but by those i needed much more luck.
Or, you can try to mix 1 dragon drone and 1 sub cruiser and 6 rogues, that could work too by this encounter, just be sure you keep the drone alive for the second wave othervise it'll be definately harder (if the sub dies, that won't be a problem for the second wave if you'd still have 5-6 units alive)!
In the second wave, don't move with the drones, the enemy will move with everything, the plasmas will hit and turn your rogues, so with their first step you already can attack the CARBs with 3 units, and your 2 unattached drones will move before the enemy in the second round too, so you easily could kill at least 2 enemy units before their first shot, 3 would be alive at most to shoot, those can't even kill 2 of yours...
