Branduil
Hero
One problem with removing iterative attacks AND giving all classes AC defense: You'd have to add a LOT of damage to each attack to make up for the damage from the lost attacks.
For instance, let's assume we have a normal 3.5 fighter. He'll probably be able to hit the enemy about 100%(actually 95) of the time on the first attack, 75% on the second, then 50%, and 25%. For damage, if he has a greatsword, and 25 STR, he'll do, on average, 7(2d6)+10(Str bonus)+5(magic wepon)+7(2d6 special magic weapon abilities like flaming or freezing)+4(Greater Weapon Spec.)=33. Adding his iterative attacks, he should do about 2.45 his average damage on each of his full attacks. That's an average of 80.85 damage each round.
If you remove iterative attacks, and make it less likely for the fighter to hit the enemy, so his first(and only) attack hits 75% of the time, even if you give him half his level in damage bonus, that's still just 43x0.75= 32.25 average damage each round. It will take a lot longer to defeat some enemies this way.
Also, changes like this really favor the Rogue since he would likely be using Spring Attack for one attack each round anyway.
For instance, let's assume we have a normal 3.5 fighter. He'll probably be able to hit the enemy about 100%(actually 95) of the time on the first attack, 75% on the second, then 50%, and 25%. For damage, if he has a greatsword, and 25 STR, he'll do, on average, 7(2d6)+10(Str bonus)+5(magic wepon)+7(2d6 special magic weapon abilities like flaming or freezing)+4(Greater Weapon Spec.)=33. Adding his iterative attacks, he should do about 2.45 his average damage on each of his full attacks. That's an average of 80.85 damage each round.
If you remove iterative attacks, and make it less likely for the fighter to hit the enemy, so his first(and only) attack hits 75% of the time, even if you give him half his level in damage bonus, that's still just 43x0.75= 32.25 average damage each round. It will take a lot longer to defeat some enemies this way.
Also, changes like this really favor the Rogue since he would likely be using Spring Attack for one attack each round anyway.