If you could humor me with the actual relevant stat numbers up through step 8 that would help.
Mark I Fighter
Cap health: 15.840.000
Cap dps: 97.920
Cap dps with bonus: 587.520
Mark II Fighter
Cap health: 31.680.000
Cap dps: 195.840
Cap dps with bonus: 1.175.040
Mark III Fighter
Cap health: 47.520.000
Cap dps: 293.760
Cap dps with bonus: 1.762.560
Mark IV Fighter
Cap health: 63.360.000
Cap dps: 391.680
Cap dps with bonus: 2.350.080
Mark I MRLS Guard Post
Health: 3.000.000
dps: 99.750
dps with bonus: 598.500
Mark II MRLS Guard Post
Health: 6.000.000
dps: 199.500
dps with bonus: 1.197.000
Mark III MRLS Guard Post
Health: 9.000.000
dps: 299.250
dps with bonus: 1.795.500
Mark IV MRLS Guard Post
Health: 12.000.000
dps: 399.000
dps with bonus: 2.394.000
Fighters vs MRLSsMark I Fighters destroy Mark I MRLS Guard Post in 5,1 seconds
Mark I MRLS Guard Post destroys Mark I Fighters in 26,5 seconds
In 5,1 seconds MRLS Guard Post does 3.056.066 damage and destroys 19 Fighters
The first burst from the MRLS will destroy some of the Fighters so the MRLS wont be destroyed exactly in 5,1 seconds.. and Fighters have 4 second reload time. MRLS also have much longer range than Fighters so the MRLS will get to shoot at least 1 burst before Fighters are able to shoot.. so it will do about 3.654.566 damage and destroy 22 Fighters.. and again.. Fighters die so the MRLS wont be destroyed in 5,1 seconds so the MRLS will destroy about 26 fighters.. which is 27% of the cap. Luckily Fighters are cheap. A cap of them costs only 38.400 resources.
If you are unlucky and get a MarkIV AI planet adjacent to your home world.. it would be Mark I Fighters vs Mark IV MRLS.
Mark IV MRLS would destroy all Mark I Fighters in about 7 seconds. In 2 bursts in other words. Most of the Fighters wouldn't even get to shoot because MRLS has much longer range.
Caps of Mark I and Mark II Fighters destroy Mark IV MRLS Guard Post in 7 seconds (This is same as MarkIII Fighters vs MarkIV MRLS)
Mark IV MRLS Guard Post destroys Mark I and Mark II Fighters in 20 seconds
Mark IV MRLS will do about 19.152.000 damage and destroy about 39 Mark III Fighters which is about 41% of the cap.
Add AI ships guarding the MRLS and the Wormhole the fighters came trough and the fighters will probably lose.
Bombers vs Missile Guard PostMark I Bomber
Cap health: 14.976.000
Cap dps: 78.080
Cap dps with bonus: 468.480
Mark I Heavy Bomber Starship
Cap health: 36.000.000
Cap dps: 300.000
Btw. Bomber Starship's description is outdated. It still says "but unable to hit smaller targets" even though it can.
Mark I Missile Guard Post
Health: 3.000.000
dps: 80.000
dps with bonus: 480.000
Mark IV Missile Guard Post
Health: 12.000.000
dps: 320.000
dps with bonus: 1.920.000
Mark I Bombers destroy Mark I Missile Guard Post in 6 seconds
Mark I Missile Guard Post will destroy Mark I Bombers in 31 seconds
Since Missile Guard Posts have crazy range they will get to shoot at least 3 times before Bombers get to shoot. So the Missile Guard Post will do about 4.320.000 damage and destroy about 28 Bombers before the bombers get to shoot. 96-12=68 so the new "dps with bonus" is 331.840. With that dps they would destroy the MGP in 9 seconds. In 9 seconds MGP does 4.320.000 damage and destroy about 28 Bombers. In total about 56 Bombers will be destroyed. That's about 58% of the cap. This would get VERY expensive.
Mark IV Missile Guard Post would destroy about 64 Mark III Bombers. Well.. that's in theory. Since some of the bombers would be destroyed after every burst AND there would be AI ships guarding the GP and the Wormhole the bombers would have NO chance vs the Mark IV Missile Guard Post.
Mark IV Missile Guard Post would destroy 2 Bomber Starships in about 19 seconds.
The Bombers SSs would destroy the MIV MGP in about 40 seconds. So um.. yeah.
It seems like Needler and Laser Guard Post is THE WORST (op). Maybe even worse than Missile Guard Post. They both have same DPS but Laser is a bit worse because it reloads faster.
Health: 3.000.000
dps: 100.000
dps with bonus: 600.000
Mark I Needler would destroy a cap of Missile Frigates in 25 seconds and Mark I Laser would destroy Bombers in 25 seconds too.
EDIT: In a counter vs counter fight the Guard Post should lose and destroy about 15% or 20% of the fleet ships. At the moment moment the Guard Post destroys like 27% - 60% depending on Guard Post. The main problems are Mark IV AI planets adjacent to the player's home planet and Missile-, Needler- and Laser Guard Posts.