Armor issuse, Protective + X

[Berf]

The Drones are often heavily protected, but it doesn't make them invulnerable. Just make sure you hit them hard enough
I'd say don't bother to fight a Pr +2 without at least a CBT 5 fighter. Keep staking the attacks (you should have more fighters than the ISC, so focus on one Drone at a time) or produce some heavy artillery (Bamaka are very good at this). In fact, Bamaka and Matriarchy can fight back quite decently and Jokers can mix close combat (Yorg, Vladd) and range attacks (Bogdana's poisoning, Explosives,etc.) for good results. Convoy is a little bit at a disavantage when fighting ISC (good assets are Friedrich, Otto and Heinrich, but they need backups), so just avoid fighting and choose a Mission accordingly. The Resistance, well, they're new so it can be hard, but they have a very decent fighter (Ashton) and a very valuable shooter (Courteney).
Anyway, if you don't think you can outmatch Drones in fights, just play the right Mission, or use the good Tactical card