Basically archers can do everything a melee focused warrior can about as well as the melee warrior, but with the added benefit of being able to perform incredibly well at range.
IMHO, the way the game is designed, the ranged warrior shouldn't even be close to the damage of the melee warrior. If the ranged warrior was truly squishy or truly pathetic in melee combat I might understand them having similar damage. But that simply isn't the case. Fighting styles and feats complete negate any potential penalties the ranged warrior might face.
This harkens back to the entire fundament of the fantasy genre.
First off: D&D uses hit points. In real-life even a single attack that hits can cripple you, so the basic (but almost forgotten) function of hit points is to make sure you don't go down by a single hit, since this is an absolute requirement for a game that asks players to make melee builds.
But that is not enough. You need more game mechanics to favor melee for melee to actually be the logical choice (and not just the fun choice, the colorful choice etc).
I believe that melee warriors should have 10-20% more effective HP and 10-20% more damage than an a ranged warrior given the difficulty most melee warriors face in combat (flying enemies, opportunity attacks, being knocked prone, enemies at range greater than 30ft, enemies spread out more than 30 ft, choice targets in the back ranks, etc). Instead, archers tend to deal more damage and have similar defenses.
This is why some games make it difficult for an archer to wear heavy armor.
I don't think a mere 20% delta is enough. At high levels, that means that if ranged combat do 50 DPR, melee combat should do 60 DPR. Assuming this figure doesn't take range into account, I believe it is not enough. Remember, every time the melee fighter can't reach a new foe, his DPR drops precipitously.
I'm afraid that to truly relegate ranged combat to a secondary function, and to do so purely by regulating damage, the melee build probably needs to do DOUBLE damage of ranged.
But that's probably not a good solution. Or more accurately, it's an extreme solution that's really not needed.
Because you have other parameters to play with. Just by disabling ranged fire when in melee you go a long way of decreasing the attractiveness of the "ranged only" build.
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In the end I should say:
* remove the ability to negate the disadvantage for shooting when within 5 ft from an enemy completely from the game, so there is no way to get around that penalty
* revert the decision to allow ranged combatants to add dexterity to damage.
I would probably skip 3rd edition's rule and go straight to a rule where you always add strength to damage, no matter what weapon you're using (since that is what 3E's "compound" bows led to in the end after all). I would still allow Finesse weapons to supersede this rule and add Dex damage - I'm not trying to hose the swashbucker, just to put a check on actual ranged builds.
And you're done.
Do note how this involves absolutely no homecooked untested rules. My suggestion just removes one ill-conceived feat ability, and then reverting to a tried and tested D&D tradition that has worked well for decades!
