while we are on topic of Swarm, what is the range of their weapons?
I believe Soldiers have a range around 120,000km (modified by your ECM). When dealing with large swarms, the route I went was to build a laser gunboat with multiple 30-35cm lasers shrunk down by 0.75 or 0.5. Slap a bunch of those on a ship (say, 12?) with long-range, high-speed fire controls for each laser seperately. Because of the long recharge time, you don't need a very big reactor. Then put a decent ECM on it. THEN (and this part is important) make sure it has enough thrust to exceed 10000 km/s.
The drones will charge right at you. Head away from them at less than full thrust and slowly let them come into range of your lasers, but outside range of their mesons. Then you can just whittle away at their numbers for how ever long it takes. The reason I like 30-35cm lasers is that the damage is generally enough to vaporize a drone if it hits. The alternative is that you hit and cripple a bunch, leaving them motionless. Then, after you kill off the last mobile one, you reverse course and sweep your way back through all the crippled ones, finishing them off.
I had good results with a design like this, until I got greedy and tried to let them close the distance just a bit more to increase my accuracy. Turned out I had misjudged their range. When you're talking about a swarm of 70-80 drones, even a 5% chance to hit is going to get in a few lucky hits. And when those hits take out engines....yeah, you're pretty much fucked.
The alternative is to missile spam like a boss.