There was something on Slashdot a couple days back about arming drones with frickin' lasers. Not for vaporizing targets on the ground, mind you, but so they could zap incoming anti-drone missiles out of the sky!
Only, as an early commenter pointed out, even the little excerpt mentioned that the lasers were for defense against "EO/IR guided surface-to-air missiles," so 'twas pretty clear that the idea was to blind optical seekers.
Now, if you know what type of lasers all the drones are equipped with, protecting your seeker against it is easy. Even if not, or if they're equipped with different types of lasers, or even with tunable lasers: think auto-darkening welding helmet. If it suddenly gets bright, make the filter enough darker to prevent damage.
In combination with which: if you're tracking a target, and suddenly get dazzled by coherent light, follow the coherent light.
Now, if the lasers were attached to "smart chaff" being dropped by the drones, following the light would be counterproductive... but chaff that can track an incoming missile and keep a laser pointed at it is going to be expensive and in short supply. And you can keep firing dumb rockets at the drones until the dronemaster runs out of money.