Having come to this game from Starfire (and David Weber novels), it is weird to me to not mount Point Defense of some kind on most ship classes, but I can certainly take advice and go in a different direction. Gauss turrets are huge.
I was hoping medium sized laser turrets could double as antiship and antimissile weapons in sufficient numbers but I can ditch them in favor of just straight lasers for anti-ship purposes and Gauss-equipped PD ships.
Aurora is usually viewed as a space combat 4x game. However, it is also very much a role-playing and story-telling game. Therefore, if you believe that every ship should have at least some point defence, then design them that way. I tend to run campaigns around a theme, such as WH40k or Battlestar Galactica, etc. and then design ships to match the theme. Once the game gets underway, designs evolve based on need and combat experience in that particular game. You will get some excellent advice on these forums about how to avoid common mistakes on ship design and the many factors that need to be considered as a factor in design and how those factors should be weighted in different situations. However my advice is not to get too hung up on 'optimal' designs. Just build what feels right for your vision of your Empire and experience will drive future designs.
For example, here is a Lunar class cruiser from my current campaign. It has two types of offensive energy weapons, a battery of point defence weapons, six missile tubes and a hangar bay. It is definitely not an 'optimal' design, although at 37,500 tons it can get away with it. It is also not intended for solo operations and would function as part of a fleet. Below that is a much smaller frigate, with both offensive and defensive energy weapons.
Lunar class Cruiser 37,500 tons 1,120 Crew 5,623.2 BP TCS 750 TH 3,000 EM 5,520
4000 km/s Armour 6-99 Shields 184-368 HTK 220 Sensors 18/24/0/0 DCR 18-4 PPV 187.2
Maint Life 2.03 Years MSP 3,191 AFR 625% IFR 8.7% 1YR 1,034 5YR 15,512 Max Repair 375 MSP
Hangar Deck Capacity 1,000 tons Magazine 650 / 0
Captain Control Rating 2 BRG AUX
Intended Deployment Time: 12 months Flight Crew Berths 20 Morale Check Required
Ravenor Drive Systems RDS-750B Gas-Core Drive (4) Power 3000 Fuel Use 49.92% Signature 750 Explosion 12%
Fuel Capacity 1,603,000 Litres Range 15.4 billion km (44 days at full power)
Valentinian-Stern VS-46 Void Shield (4) Recharge Time 368 seconds (0.5 per second)
Astaroth Kinetics AK-20 Weapons Battery (12x4) Range 160,000km TS: 4,000 km/s Power 12-4 RM 40,000 km ROF 15
Valentinian-Ventris V4-200 Lance Battery (4) Range 200,000km TS: 4,000 km/s Power 10-3.5 ROF 15
Astaroth Kinetics AK-10 Light Weapon Battery (12x4) Range 40,000km TS: 4,000 km/s Power 3-3 RM 40,000 km ROF 5
MK I Energy Weapon Fire Control (4) Max Range: 256,000 km TS: 4,000 km/s ECCM-0 96 92 88 84 80 77 73 69 65 61
MK I Light Energy Weapon Fire Control (2) Max Range: 80,000 km TS: 4,000 km/s ECCM-0 88 75 62 50 38 25 12 0 0 0
R-24B Gaseous Fission Reactor (4) Total Power Output 98.1 Exp 5%
MK I Standard Torpedo Launcher (6) Missile Size: 12 Rate of Fire 175
MK I Small Target Fire Control (1) Range 27.5m km Resolution 10
MK I Torpedo Fire Control (1) Range 89.1m km Resolution 120
MK I Standard Torpedo (54) Speed: 25,000 km/s End: 5.3m Range: 8m km WH: 12 Size: 12 TH: 83/50/25
MK I Torpedo Detection Array (1) GPS 16 Range 6.4m km MCR 574.5k km Resolution 1
MK I Cruiser Active Augur Array (1) GPS 15360 Range 89.1m km Resolution 120
MK I Large Thermal Augur Array (1) Sensitivity 18 Detect Sig Strength 1000: 33.5m km
MK I Large Electromagnetic Augur Array (1) Sensitivity 24 Detect Sig Strength 1000: 38.7m km
Strike Group
1x Thunderhawk Assault Transport Speed: 9504 km/s Size: 19.99
Sword class Frigate 9,375 tons 306 Crew 1,521.3 BP TCS 187 TH 750 EM 1,380
4000 km/s Armour 4-39 Shields 46-368 HTK 65 Sensors 6/8/0/0 DCR 5-5 PPV 46
Maint Life 2.36 Years MSP 507 AFR 141% IFR 2.0% 1YR 125 5YR 1,870 Max Repair 187.5 MSP
Commander Control Rating 2 BRG AUX
Intended Deployment Time: 12 months Morale Check Required
Ravenor Drive Systems RDS-375B Gas-Core Drive (2) Power 750 Fuel Use 70.60% Signature 375 Explosion 12%
Fuel Capacity 650,000 Litres Range 17.7 billion km (51 days at full power)
Valentinian-Stern VS-46 Void Shield (1) Recharge Time 368 seconds (0.1 per second)
Astaroth Kinetics AK-20 Weapons Battery (4x4) Range 160,000km TS: 4,000 km/s Power 12-4 RM 40,000 km ROF 15
Astaroth Kinetics AK-10 Light Weapon Battery (6x4) Range 40,000km TS: 4,000 km/s Power 3-3 RM 40,000 km ROF 5
MK I Light Energy Weapon Fire Control (2) Max Range: 80,000 km TS: 4,000 km/s ECCM-0 88 75 62 50 38 25 12 0 0 0
MK I Energy Weapon Fire Control (2) Max Range: 256,000 km TS: 4,000 km/s ECCM-0 96 92 88 84 80 77 73 69 65 61
R-17 Gaseous Fission Reactor (2) Total Power Output 34.5 Exp 5%
MK I Frigate Active Augur Array (1) GPS 5760 Range 54.5m km Resolution 120
MK I Torpedo Detection Array (1) GPS 16 Range 6.4m km MCR 574.5k km Resolution 1
MK I Electromagnetic Augur Array (1) Sensitivity 8 Detect Sig Strength 1000: 22.4m km
MK I Thermal Augur Array (1) Sensitivity 6 Detect Sig Strength 1000: 19.4m km
This design is from a recent BSG campaign. It is carrier-warship hybrid, which again is not intended as an optimal design. Generally carriers are built to stay out of combat and good advice would be to minimize defences and maximise hangar space. Alternatively, if you are building a warship for energy-range combat, then don't waste a lot of internal space on hangars. In this case, the design was to match the lore, so it had both fighters and railguns and actually proved to be very effective anyway. Although once again size helps a lot. Later versions actually increased close combat capability. Here is the campaign:
http://aurora2.pentarch.org/index.php?topic=12909.0Galactica class Battlestar 75,000 tons 1,465 Crew 9,093.3 BP TCS 1,500 TH 4,800 EM 0
3200 km/s Armour 8-158 Shields 0-0 HTK 372 Sensors 12/12/0/0 DCR 53 PPV 149.28
Maint Life 2.04 Years MSP 4,016 AFR 849% IFR 11.8% 1YR 1,290 5YR 19,356 Max Repair 300.00 MSP
Hangar Deck Capacity 24,000 tons
Commander Control Rating 3 BRG AUX ENG
Intended Deployment Time: 12 months Flight Crew Berths 480 Morale Check Required
Zeus Drive Systems ZDS-600 Gas Core Drive (8) Power 4800.0 Fuel Use 32.66% Signature 600.00 Exp 10%
Fuel Capacity 3,269,000 Litres Range 24 billion km (86 days at full power)
Ares Kinetics AK-20 Railgun (12x4) Range 160,000km TS: 4,000 km/s Power 12-3 RM 40,000 km ROF 20
Ares Kinetics G20-8 Gauss Cannon Turret (4x8) Range 20,000km TS: 16000 km/s RM 20,000 km ROF 5
Hyperion R256-S4 Beam Fire Control (2) Max Range: 256,000 km TS: 4,000 km/s
Hyperion R64-S16 Beam Fire Control (2) Max Range: 64,000 km TS: 16,000 km/s
R-18 Gaseous Fission Reactor (2) Total Power Output 36.5 Exp 5%
Artemis-70 Active Sensor (1) GPS 12960 Range 70.8m km Resolution 120
Artemis-5M Missile Detection Sensor (1) GPS 12 Range 4.8m km MCR 430.9k km Resolution 1
Themis EM-12 Passive Sensor (1) Sensitivity 12 Detect Sig Strength 1000: 27.4m km
Themis TH-12 Passive Sensor (1) Sensitivity 12 Detect Sig Strength 1000: 27.4m km
Strike Group
4x Raptor-S Scout Speed: 3201 km/s Size: 19.99
2x Raptor-M Assault Transport Speed: 7003 km/s Size: 19.99
60x Viper MK I Fighter Speed: 8001 km/s Size: 6
In summary, I would design what feels right for the style of Empire you are building. If you want to replicate Honorverse-style ships, then go ahead. Its your game. This is not a criticism BTW of the excellent advice provided in this thread. I'm just stating a different option, which is to let role-playing drive your choices. Over time, combat experience will inform your future design choices.