First, Manyshot:

Manyshot. One of the feats in DDO that I am sure gives devs cold sweats when they are developing new ranged combat abilities and feats. You'll find that if they stuck with the original 3.5 SRD, that all the problems they worry about would go away.

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Manyshot

Prerequisites: Dex 17, Point Blank Shot, Rapid Shot, base attack bonus +6

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.

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.

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That bolded text above means that all arrows after the first in a volley have NO CHANCE of critting. This makes manyshot as a toggle very manageable, and tempers its ability to be overpowered by other abilities.

Basically, this means Manyshot should be several toggles: Manyshot +1, Manyshot +2, and Manyshot +3 (perhaps a Manyshot +4 for high level epic toons.) Each toggle would infer either a negative chance to hit, or a flat percentage chance that the shot is a miss regardless of roll result. To balance it for the mechanics of DDO, I'd suggest that the penalty for the first shot be 0, with an increasing negative to hit per arrow fired after. For example, a -0% BaB for the first arrow, -10% BaB for the second, -20% BaB for the third, and -30% BaB for the fourth. Alternatively, you can infer a 0/10/20/30% chance of outright missing regardless of roll.

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Now, Ten Thousand Stars

It's obvious to me that ten thousand stars was meant to be for shuriken, but I understand that restricting a feat to a single exotic throwing weapon would hamstring its already marginal usefulness, given there are only five types of throwing weapons in total. I'd suggest opening up 10,000 stars to all throwing weapons, but disallowing its effect on arrows or bolts. It should be a clicky which throws 10 projectiles at once and refreshes every 30 seconds.

A pretty simple solution there, but one I believe is needed.