Here's another similar analysis of THF vs TWF in various stages, for comparison or whatever.
Generic 10th level Fighter with either a single +3 weapon or dual +2 weapons (similar cost).
Numbers in [...] brackets show additional damage with full off-hand Strength bonus.
Fighter
10th Level
Str 22
Weapon Focus (greatsword)
Weapon Specialization (greatsword)
Power Attack
<+7 Feats>
+3 greatsword attack +20/+15 damage 2d6+14
avg. damage vs AC 20:
36.75 (PA2: 41.25) (PA5: 41.85) (PA10: 34.85)
avg. damage vs AC 25:
28.35 (PA2: 28.75) (PA5: 26.35) (PA10: 14.35)
avg. damage vs AC 30:
17.85 (PA2: 16.25) (PA5: 10.85) (PA10:
_4.1)
Fighter
10th Level
Str 22
Weapon Focus (short sword)
Weapon Specialization (short sword)
Two-Weapon Fighting
Improved Two-Weapon Fighting
<+6 Feats>
+2 short sword attack +17/+12 damage 1d6+10
+2 short sword attack +17/+12 damage 1d6+7[+3]
avg. damage vs AC 20:
37.2 [+4.65=
41.85]
avg. damage vs AC 25:
25.2 [+3.15=
28.35]
avg. damage vs AC 30:
13.2 [+1.65=
14.85]
Fighter
10th Level
Str 22
Weapon Focus (longsword)
Weapon Specialization (longsword)
Two-Weapon Fighting
Improved Two-Weapon Fighting
(Power Attack)
<+6(5) Feats>
+2 longsword attack +15/+10 damage 1d8+10
+2 longsword attack +15/+10 damage 1d8+7[+3]
avg. damage vs AC 20:
35.1 [+4.05=
39.15] (PA2: 34.5) (PA5: 30.6) (PA10: 16.1)
avg. damage vs AC 25:
22.1 [+2.55=
24.65] (PA2: 19.5) (PA5: 12.6) (PA10:
_4.6)
avg. damage vs AC 30:
_9.1 [+1.05=
10.15] (PA2:
_7.5) (PA5:
_3.6) (PA10:
_4.6)
Fighter
10th Level
Str 22
Exotic Weapon Proficiency (bastard sword)
Weapon Focus (bastard sword)
Weapon Specialization (bastard sword)
Two-Weapon Fighting
Improved Two-Weapon Fighting
Oversized Two-Weapon Fighting
(Power Attack)
<+4(3) Feats>
+2 bastard sword attack +17/+12 damage 1d10+10
+2 bastard sword attack +17/+12 damage 1d10+7[+3]
avg. damage vs AC 20:
43.4 [+4.65=
48.05] (PA2: 43.2) (PA5: 39.9) (PA10: 26.4)
avg. damage vs AC 25:
29.4 [+3.15=
32.55] (PA2: 27.2) (PA5: 20.9) (PA10:
_9.6)
avg. damage vs AC 30:
15.4 [+1.65=
17.05] (PA2: 11.2) (PA5:
_7.6) (PA10:
_4.8)
I also don't think it would be bad to allow the full Strength bonus, TWF is costly enough as is.
And Power Attack simply isn't worth it, when fighting with two weapons.
Bye
Thanee