The Cleric dip is only good if you get Travel Devotion. This allows you to take a move action as a swift action for one minute once per day. You can use Turn attempts (3 per instance, IIRC) to get more uses of this ability.
Do you have ToB?
If you do, get an aptitude enhancement on your weapon. This will allow you to apply a different weapon focus or other weapon specific feats to your actual weapon. Enter WF(Crossbow), and Crossbow Sniper from PHB2. Now you can use Precision damage at 60ft and also add 1/2 Dex mod to your damage.
A 1 level dip in H&R Fighter will allow you to add Dex to damage to flat-footed enemies within 30ft.
A 2 level dip into Targetteer Figher (Dragon Mag) will allow you to generally add Dex to damage, but it's precision damage. They are exclusive, you can only take one.
If your DM is loose on Racial requirements you might be able to take Shadowstrike from CoR, it nets you +1/+1d6 to attack and damage when in an area of shadowy illumination or darker. Normally you have to be a Krinth, though.... it's not a high-powered feat, IMHO, so....
Improved Precise Shot is critical.
Woodland Archer allows increasing attack bonuses if you miss, and other stuff. (RotW)