As I'm still poking at all the new features and haven't started my next real game, I went ahead and poked at this.
Both AI types are Viral Enthusiast in my game.
Gametime 13:35 (min:sec), warp into my first system with the Viral Cluster, it has 3 Mk II Clusters in a Mk I AI system. I attack with 198 fighters, 198 bombers (Mk I ship cap).
First cluster, on the warp point I warp in at, 37 Swarmers spawn. It spawns another wave of 5 before I'm able to destroy it.
Second cluster spawns another 37 Swarmers at 14:03 as I close. My fleet is more depleted and it spawns a wave of 5 more spawners every couple seconds until I destroy it, looked like 4 or 5 waves of 5 spawners.
Third cluster spawns 37 swarmers aswell at 15:12 as I approach. However, this time the spawn rate is different. I destroy this cluster at 15:33 game time but it was able to spawn enough smaller waves fast enough that it got up to 57 (or so) spawners alive. Note all the 37 spawners from the wave as I approached are dead, this is solely from the waves that spawned as I attacked it. I don't have any method of actually timing it in game beyond just watching, but I think it was about twice a second the small waves were spawning. Either way, it was spawning fast enough to build up to 57 spawners while my fleet was parked right on top of it.
After this 3rd cluster is cleared, I have 75 bombers and 137 fighters left.
I bring my fleet back up to full and head for the second system. It has 4 Cluster Mk II's in an AI Mk I system, but a Regeneration Chamber is present aswell (which shouldn't affect anything but....)
Warp in at 20:41, 37 Swarmers spawn. I let my fleet clear the warp point on autotarget which doesn't attack the Cluster, small waves are every few seconds. I issue the manual attack order on the Cluster, waves spawn faster. Not quite as fast as the 3rd cluster in the first system, but a noticeable increase.
Approach the second cluster at 21:16, 37 swarmers spawn. This time I delay in attacking the cluster, it is spawning 5 swarmers every 4 seconds over the 30 seconds or so I wait. Issue the attack order on the cluster, spawn rate shoots up once again.
Approach 3rd cluster at 22:20, 37 swarmers spawn. Repeat the spawn increase after the attack order, but not as much an increase as the 1st or 2nd clusters in this system.
37 swarmers spawn on approach at 22:32. This time, no spawn increase that I see once I issue the attack order although I issue it almost immediately as my fleet is small. I destroy the cluster but the other ships destroy my fleet also.
3rd system has 2 Cluster Mk IV's in an AI Mk III system.
Warp in at 30:13, a lot of swarmers spawn. I have no scouts because it's a Mk III system, but I guesstimate 150-200 swarmers spawn. And wow, this spawn rate is insane. each spawn is a fan of swarmers appearing. Again, no scout data but it's gotta be almost 100 swarmers each spawn, spawning at least once a second. 31:04 the last of my fleet is destroyed, I now have a threat meter of 3026!!! So call it 3000 swarmers or so have spawned from this one cluster in less then a minute.
And yes, my home system just got 3002 swarmers in the face, I quickly die as I didn't bother with defences in this test game.
edit: When I did the above, I hadn't noticed that the swarmers replicated so that's going to throw my numbers off somewhat. Below here I was aware though.
I can't find any Cluster Mk I or Mk III to test, but I'm thinking it's the build points on their replication is low. I don't know what the attack damage -> build point conversion is, but with the replication being on 500 points I had 3000 swarmers warp into my home system, they hit a peak of 17000 (yes seventeen thousand) by the time the are done attacking stuff. Oddly enough, they aren't attacking my command station or space dock or energy reactors, they are just sitting there. I let everything play out and the last swarmer dies at 36:22. The scoreboard shows me killing another 9280 swarmers so I don't think that's counting the ones that died to self-damage.
Note that the swarmers did attack my cryo pods and human cities in my home system aswell as all my mobile military, but they did NOT attack my command station, turrets (yes, all my turrets are still alive), harversters, science ship, manufactories, missle silo or starship constructor.
Overall the Cluster Mk II's in the first two systems were pretty reasonable really, it's this single Mk IV that's just going insane.
D.