other than hitting them from the air with AX Dumbfires, the Aphelion's by far the best option to deal with Revenants if you have steady access to ammo boxes.
Just like with vs skimmers, its kinda pain to land hits with kinetic and even bigger pain to use plasma, they move quite fast and its very likely for them to be elsewhere before plasma or bullet manages to get there.
Thermal owns them on other hand, and they dont seems like being resistant to that type of dmg. Also eclipse works very well too. Not quite sure yet, but it seems that they might have weak spot, where is thier lightblog thing located. When I was shooting it with my lasers wich do have headshot mod, when hitting its "eye", dmg was higher than dmg done into any other of its parts.
Still, with focusing laser fire into eye, I could kill about 2 revenats with single clip, and since there is only 6 of them per batch, it took about 3 mags to remove full squad of these.
Once entire batch of revenats is killed, scout will came in and drops next ones, and that seems have no limit.
For lulz, I was able to gather about 20 scouts that way, as these after droping revenats instead of waking out, they just hover about 700-800m above settlement, and ingore dmg taken from ground.
would it be more beneficial to leave just one drone alive?
It is beneficial to leave one out - as one drone is not big threat at all, you can progress with mission much easier with just single drone to worry about, and unless all of drones are gone, new ones wont appear.
It also seems that only initial batch of drones is most lethal, as they actually atleast patrol settlements and move around. If these are gone, any next ones seems being much more dumb and they kinda stuck to area where they was being droped by scout.