Balancing archery across the classes
Either remove the extended lockout timer for doubleshot on Manyshot outright, or give high level rangers a way to remove it (in the DWS core at 18 or 20, or as a granted class feature at level 15+); that will help close the gap between archers relying on doubleshot and those relying on 10K Stars. Also consider giving high level rangers either an extended Manyshot, or a reduced Manyshot cooldown.
Give rangers some new spells at 3rd and 4th levels that affect their combat abilities. The Spell Compendium has a lot of options there for both TWFing and archery. I'd like to see rangers not eclipse monkchers for archery rate of fire, but have some unique apples to oranges abilities, like AoE shots or crowd control. Leg Shot in DWS is nice, but there's too little in the tree to make it worth investing that far, and is eclipsed in epic levels by Pin and Otto's Whistler.
Give fighters an ability to use tactics feats (Stunning Blow, Improved/Trip, Improved/Sunder) at range to differentiate them from monkchers and rangers.
Provide a ranged version of Assassinate for rogues.
The problem with Ten Thousand Stars isn't that it's too good, it's that there really isn't any alternative that's worth considering. Simply upping doubleshot a bunch won't really help, because if it's made truly competitive with 10K Stars, you just relegate 10K Stars to the dung heap, since the DS will free up build decisions rather than forcing monk 6.
Look at Paizo's Pathfinder...compare the Zen Archer monk archetype to the Archer fighter archetype, and the various ranger archetypes. The ranger, despite its name, doesn't need to be the best archer--it just needs to be competitive while also offering some strong additional abilities. The switch-hitting set-up in DDO is one of the bigger draws of the ranger, but it's kind of rough essentially dumping a lot of your focus when you swap to melee, especially since there are so few places in DDO where we're strongly encouraged to put away our melee weapon(s) and pull out a ranged weapon to do anything besides hit a switch.