So you'd need serious anti-drone capabilities to get the artillery close enough, and good luck if you have it sitting around deployed for any lenghth of time.
Unless the target is low risk/value, or on the move AND low value, or (most likely) you have truly bananas amount of drone magazine to burn through. Laser mesh networks I think are also being tried, but again, that's a bunch of drones.
Another downside of fiber is the same downside as laser sighting - there is an arrow painted on the ground back to your position. The fiber is no viz to your eyeball, but not to dynamic filters on your drone's EOIR. That will get back to counterbatteries or enemy fiber drone - and if their first arty shot is a guided arty (tube or rocket) you don't get the warning of ranging "framing" shots. The WW2 experience mindset couldn't be a worse metaphor here.
Both shooting and moving is very detrimental to staying hidden. And with FPV drones moving doesn't do you much good unless you move out of drone range, which as mentioned is or very nearly is 2x the effective range of such artillery systems.
The attack drones don't have to be big, just big enough to score a mobility kill and the artillery is pretty much f'd in the a...