Jester David
Hero
The odds of rolling any given number are the same but when making two attacks you have a higher chance of one being a hit rather than none.Why would there be a bell curve? The odds of rolling each individual number are still 1in20 no matter how many dice you roll. It is only a bell curve if you were to add the dice which you are not. That is the statistical reality according to all of my stix classes, or is that the new fuzzy math they have been teaching?
I've done some Excel spreadsheets in my time where you can generate a few thousand die rolls, and rolling twice does help.
Okay, let's break it down.For each attack in twf you are decreasing your chances to hit by 10% and a (1d6+4) x 4 still will never equal 4d6+22. If you throw in power attack it is even a worse disparity. Now the chances to hit are the same and if the twf hits he is getting 4d6+40, both are more with weapon specialization. Now he is at 4d6+44! Give him furious focus and the power attack penalty goes away for the first attack.
A TWF armed with two shortswords does two attacks dealing 1d6. TWF tends to be a high Dex (which doesn't help their damage) Assuming you need a 12 to hit normally this becomes a 14 with TWF so you have a 35% chance of hitting. Average damage is 3.85 (2[5.5*.35]). Rangers are an exception but we'll work around a fighter for all the examples. Weapon specialization makes this 5.25.
A sword-n-board might be doing 1d8+4 but have a 45% chance of hitting which works out to 3.825 average damage, but higher AC. And a greatsword does 2d6+4 for 5.85 average damage. With Weapon Specialization this is 4.725 and 6.75. Adding power attack to the mix changes the damage to 5 and 7.2.
However, this is only half the story. 2h and SnB the attacks are all-or-nothing. They have the straight 40-45% chance of hitting and dealing damage. The TWF, even with the reduced 35% chance per attack has an effective 57.75% chance of landing A hit. Some damage is better than no damage.
So TWF is slightly higher damage that sword-n-board, especially with weapon spec, but less that a giant two-hander. But you take SnB for defence and a higher AC, although a single feat gets a TWF some defence.
Let's also do level 6, when iteratives come into play. AC doesn't increase at the same rate as BAB so accuracy often goes up. So the SnB & 2h fighter hits on a 12 and a 17 with Power Attack, and the TWF on a 12 and 17. We'll also give the 2h Furious Focus to really make things extreme, so the 2h hits on a 10 and 17.
SnB does an average of 6.3 and 2.8 for a total of 9.1. The 2h does and average of 11.55 on the first strike and 4.2 on the second for a total of 15.75. The TWF can make four attacks dealing 3.375, 3.375, 1.5, and 1.5 for a total of 9.75.
So TWF continues to hold even with one handed weapons on average expected damage. Which seems pretty balanced.
But this also isn't going ranger, which might have higher Strength or rogue that would add Sneak Attack to the mix.