Here's how combat would work if the "Dexterity controls all attack rolls" rule were implemented.
I've taken the Otis v. Fred, Harold, & Warren fight, used the same rolls, and applied the modifiers differently.
Also, I realized that 3.5E handles weapon finesse a little differently than 3.0E, so I applied a -1 penalty for Harold's buckler and made his short sword small size.
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Pertinent Statistics
Fred the Fighter – 5th level
Attack: +8 (+5 base, +1 Dexterity, +1 masterwork, +1 weapon focus)
Defense: +8 (+5 base, +1 Dexterity, +2 heavy steel shield)
Soak: +10 (+2 Constitution, +8 full plate)
Damage: bastard sword, 1d10 + 5 (+3 strength, +2 specialization)
Harold the Halfling Rogue – 5th level
Attack: +8 (+4 base, +4 Dexterity, +1 enhancement, -1 buckler)
Defense: +11 (+5 base, +4 Dexterity, +1 buckler, +1 size)
Soak: +0 (+1 Constitution, +3 studded leather, -4 size)
Damage: small short sword, 1d4 + 1 (+4 Dexterity (weapon finesse), +1 enhancement, -4 size)
Special: Sneak Attack +6
Warren the Wizard – 5th level
Attack: +4 (+2 base, +2 Dexterity)
Defense: +4 (+2 base, +2 Dexterity)
Soak: +2 (+1 Constitution, +1 Bracers of Armor)
Damage: quarterstaff, 1d6
Otis the Ogre
Attack: +3 (+4 base, -1 size, -1 Dexterity, +1 weapon focus)
Defense: +2 (+4 base, -1 size, -1 Dexterity)
Soak: +16 (+3 Constitution, +4 size, +5 natural armor, +3 hide armor, +1 toughness)
Damage: greatclub, 2d8 + 9 (+5 Strength, +4 size)
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Fred wins initiative and swings at Otis with his bastard sword.
Fred (attack): rolls 18
Otis (defense): rolls 9
Fred hits with an 7 point margin of success. Not enough for a critical hit.
Fred rolls his damage: 1d10 + 5 + 7 (margin of success) = 16 points – 16 (Otis’ Soak) = 0. Otis shrugs off the blow.
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Harold sneaks up behind Fred, flanks, and performs a sneak attack on Otis.
Harold (attack): rolls 17
Otis (defense): rolls 11
Harold hits with a 6 point margin of success. He does not make a critical hit.
Harold rolls his damage: 1d4 + 1 + 6 (sneak attack) + 6 (margin of success) = 15 points – 16 (Otis’ Soak) = no damage. Again, Otis shrugs off the blow.
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Otis attacks Fred, the real threat.
Otis (attack): 21
Fred (defense): 12
Otis hits with a 9 point margin of success. No critical.
Otis rolls damage: 2d8 + 9 + 9 (margin of success) = 26 points – 10 (Fred’s Soak) = 16 points of damage.
Fred is disabled.
In this version of the combat, Fred gets to crawl away…
And get killed later by Otis.
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Warren panics and casts fireball, thinking, “Well, Harold does have evasion and a good Reflex save….”
In the normal rules, Warren would roll 5d6 for his fireball. Under the GnG rules, he rolls 4d6 + 2 and inflicts 18 points of damage. Otis’ Soak absorbs 16 points, so Otis suffers only 2 points of damage. This fills in two more pips and brings him to Moderately Wounded. He suffers a -1 penalty on most rolls.
Harold does make his saving throw, but he’s not too happy about the fireball.
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Harold curses Warren. Though Harold no longer flanking Otis and loses the sneak attack, Harold attacks again.
Harold (attack): 20
Otis (defense): 6
Harold hits with a 14 point margin of success. It threatens a critical hit and selects, “Bypass Natural Armor.” Harold rolls to confirm and gets a 16, while Otis rolls 12. Otis is forced to make a Reflex save against DC 13. Bad luck for Harold! Otis rolls 19.
Go, ogre!
Uh, I mean, poor Harold!
Harold rolls his damage: 1d4 + 1 + 14 (margin of success) = 18 – 16 (Otis’ soak) = 2 points of damage. Otis is Lightly Wounded.
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Otis beats Harold like a drum.
A squishy, screaming, fluid-filled, bone-supported drum.
Otis (attack): 22
Harold (defense): 21
Otis wins by a margin of 1. Not enough for a critical hit, but plenty to ruin Harold’s day.
Otis rolls damage: 2d8 + 9 + 1 (margin of success) = 18 – 0 (Harold’s soak) = 18 points of damage.
Goody! This time Harold is only disabled!
Otis will kill him later.
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Shortly after soiling himself and wondering if CR 3 still means the same thing in the GnG system, Warren tries an acid arrow against Otis.
Warren (+4 for ranged touch attack): 24
Otis (defense): 14
Warren hits with a 10 point margin of success. He threatens a critical hit! He selects “Bypass Natural Armor” and rolls to confirm: Warren gets 18. Otis gets 4. Warren confirms the hit and ignores the Soak from Otis’ natural armor.
Warren rolls for damage: 2d4 + 10 = 15 – 11 (Otis’ Soak without Natural Armor) = 4 points of damage. Otis loses 4 more life pips. Now, he’s Moderately Wounded (-1 on most rolls).
And angry!
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Otis charges Warren!
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Lucky Warren! He gets to make an attack of opportunity against the charging Otis. Screaming like a girl-child, he swings his staff.
Warren (attack): 19
Otis (defense): 13
Warren hits with a 6 point margin of success. Not a critical hit!
Warren rolls damage: 1d6 + 6 (margin of success) = 9 – 16 (Otis’ Soak) = NO DAMAGE!
Yeah!
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Otis completes his charge.
Otis (charge, attack): 15
Warren (defense): 9
Otis gets a 6 point margin of success. No critical hit.
Otis rolls his damage: 2d8 + 9 + 6 (margin of success) = 30 – 2 (Warren’s Soak) = 28 points of damage. Warren dies instantly.
Good news! Warren didn’t get a disabled head in this version of the combat!
Bad news! Warren is still dead!
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The main difference: Fewer critical hits.
Harold still can't get a decent hit on the Ogre.
Fred gets the shaft on his attack roll.
Otis really gets the shaft on his attack roll. He doesn't instantly kill folks, just disables them.
Maybe making Dex the only stat for attack rolls isn't such a big deal...