[condensedcrab]

At long distances the small cross section of the drone requires tight focusing (expensive optics) or a high power, preferably pulsed laser (expensive laser) or both.

Not impossible but many times more expensive than the drone

[tjoff]

Expensive is fine since it is reusable.

[rdtsc]

At some point it itself becomes a target. It has to be able to get almost 100% kills, otherwise the enemy can swarm it with cheap drones, destroy the expensive installation, then continue as before.

[tjoff]

Sure, but it needs many "many times" for that to be a factor.

And even in the case it could be useful as an addition to or paired with a tank etc.

[rdtsc]

Many times more is about what it comes out to. There are some companies selling laser defense systems but they are many times more than cheap FPV drones with grenades attached.