Archery in this game is just messed up, starting with the Rate of Fire. The simple fact is that bows should have the same attack speed as melee weapons. One shot with a bow is a Standard Action, the same as one swing of a long sword. So the first step to fixing archery is correcting this mistake.

Manyshot [General]
Prerequisites
Dex 17, Point Blank Shot, Rapid Shot, base attack bonus +6

Benefit
As a standard action, you may fire two arrows at a single opponent within 30 feet. Both arrows use the same attack roll (with a -4 penalty) to determine success and deal damage normally (but see Special).

For every five points of base attack bonus you have above +6, you may add one additional arrow to this attack, to a maximum of four arrows at a base attack bonus of +16. However, each arrow after the second adds a cumulative -2 penalty on the attack roll (for a total penalty of -6 for three arrows and -8 for four).

Damage reduction and other resistances apply separately against each arrow fired.

Special
Regardless of the number of arrows you fire, you apply precision-based damage only once. If you score a critical hit, only the first arrow fired deals critical damage; all others deal regular damage.

A fighter may select Manyshot as one of his fighter bonus feats.

A 6th-level ranger who has chosen the archery combat style is treated as having Manyshot even if he does not have the prerequisites for it, but only when he is wearing light or no armor.
That's how Manyshot works in 3E.

Manyshot
Cooldown: 2 minutes
Usage: Active
Prerequisite: Dexterity 17, Point Blank Shot, Rapid Shot, and Base attack bonus +6
Description
For the next 20 seconds, add 120 to your Doubleshot and {4x your Base Attack Bonus} to Ranged Power. Cooldown: 2 minutes.

Notes
This feat does not work with thrown weapons or crossbows.
Rangers receive this feat for free at level 6, even if the prerequisites are not met.
Using this ability places Ten Thousand Stars on a 30 second cool-down if its current cool-down is less than 30 seconds.
Tip: Increase your Base attack bonus, for example using Tenser's Transformation, to receive maximum benefit from this feat.
A Fighter may select this feat as one of his fighter bonus feats.
That's how Manyshot works in DDO.

This is how Manyshot SHOULD work in DDO:
Manyshot
Usage: Toggle
Prerequisite: Dexterity 17, Point Blank Shot, Rapid Shot, Base Attack Bonus +6

Description: When you toggle Manyshot on, you gain a Competence bonus to Doubleshot and Ranged Power based on your Base Attack Bonus, but also suffer a penalty to hit:

BAB Doubleshot Attack Penalty
+6 - +11 +50% -4
+12 - +16 +75% -6

While toggled on, you gain a Ranged Power bonus equal to your Base Attack Bonus x2.