Why is this so good? (i.e., what is wrong with it?)

My design for a US/CL/1941 design is so good, I have to ask "what did I do wrong?" The design seems too good to be true. The ship carries 15-6in QF, 12-5in DP, and 48-40mm AA gus at a speed of 35 knots. The range is 8,500nm at 17 knots. I would think that the protection is adequate, by the standard of ships actually built. This is the Springsharp report:

US/CL/1941, United States Light Cruiser laid down 1941 (Engine 1950)

Displacement:
 13,114 t light; 13,632 t standard; 15,286 t normal; 16,609 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (660.91 ft / 654.00 ft) x 67.00 ft x (22.00 / 23.45 ft)
 (201.45 m / 199.34 m) x 20.42 m  x (6.71 / 7.15 m)

Armament:
      15 - 6.00" / 152 mm 55.0 cal guns - 116.57lbs / 52.88kg shells, 150 per gun
   Quick firing guns in turret on barbette mounts, 1941 Model
   5 x Triple mounts on centreline ends, majority forward
  2 raised mounts - superfiring
      12 - 5.00" / 127 mm 38.0 cal guns - 59.33lbs / 26.91kg shells, 150 per gun
   Dual purpose guns in deck and hoist mounts, 1941 Model
   6 x Twin mounts on sides, forward deck aft
  2 raised mounts - superfiring
      48 - 1.57" / 40.0 mm 55.0 cal guns - 2.00lbs / 0.91kg shells, 150 per gun
   Anti-air guns in deck mounts, 1941 Model
   8 x Quad mounts on sides, aft deck forward
  4 raised mounts - superfiring
      Weight of broadside 2,557 lbs / 1,160 kg

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 4.00" / 102 mm 435.00 ft / 132.59 m 12.00 ft / 3.66 m
 Ends: Unarmoured
   Main Belt covers 102 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  0.80" / 20 mm 435.00 ft / 132.59 m 22.00 ft / 6.71 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 4.00" / 102 mm 3.00" / 76 mm  4.00" / 102 mm
 2nd: 1.00" / 25 mm 1.00" / 25 mm  1.00" / 25 mm

   - Armoured deck - multiple decks: 3.00" / 76 mm For and Aft decks
 Forecastle: 3.00" / 76 mm  Quarter deck: 3.00" / 76 mm

   - Conning towers: Forward 4.00" / 102 mm,  Aft 0.00" / 0 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 135,115 shp / 100,796 Kw = 35.00 kts
 Range 8,500nm at 17.00 kts
 Bunker at max displacement = 2,977 tons

Complement:
 686 - 893

Cost:
 £7.285 million / $29.140 million

Distribution of weights at normal displacement:
 Armament: 651 tons, 4.3 %
 Armour: 3,541 tons, 23.2 %
    - Belts: 861 tons, 5.6 %
    - Torpedo bulkhead: 283 tons, 1.9 %
    - Armament: 553 tons, 3.6 %
    - Armour Deck: 1,790 tons, 11.7 %
    - Conning Tower: 53 tons, 0.3 %
 Machinery: 3,232 tons, 21.1 %
 Hull, fittings & equipment: 5,689 tons, 37.2 %
 Fuel, ammunition & stores: 2,173 tons, 14.2 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   22,862 lbs / 10,370 Kg = 211.7 x 6.0 " / 152 mm shells or 2.9 torpedoes
 Stability (Unstable if below 1.00): 1.11
 Metacentric height 3.4 ft / 1.0 m
 Roll period: 15.3 seconds
 Steadiness - As gun platform (Average = 50 %): 54 %
   - Recoil effect (Restricted arc if above 1.00): 0.52
 Seaboat quality  (Average = 1.00): 1.07

Hull form characteristics:
 Hull has a flush deck,
   an extended bulbous bow and large transom stern
 Block coefficient (normal/deep): 0.555 / 0.566
 Length to Beam Ratio: 9.76 : 1
 'Natural speed' for length: 29.06 kts
 Power going to wave formation at top speed: 60 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 9.00 degrees
 Stern overhang: 2.00 ft / 0.61 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 20.00 %,  31.00 ft / 9.45 m,  26.00 ft / 7.92 m
    - Forward deck: 30.00 %,  26.00 ft / 7.92 m,  23.00 ft / 7.01 m
    - Aft deck: 35.00 %,  23.00 ft / 7.01 m,  23.00 ft / 7.01 m
    - Quarter deck: 15.00 %,  23.00 ft / 7.01 m,  24.00 ft / 7.32 m
    - Average freeboard:  24.53 ft / 7.48 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 121.5 %
  - Above water (accommodation/working, high = better): 210.4 %
 Waterplane Area: 31,990 Square feet or 2,972 Square metres
 Displacement factor (Displacement / loading): 122 %
 Structure weight / hull surface area: 116 lbs/sq ft or 568 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.95
  - Longitudinal: 1.60
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent