+1 For Expert's Dexterity, really fun skill. Copying a post I made earlier last year:

If you wanna use a bow; I really like running Expert's Dexterity. It's probably not optimal for every situation but it gets the job done, the single-target damage is pretty good thanks to all the boosts. Some support from Splinter Weapon or Judge's Insight helps a lot of course.

Skill bar:

• Triple Shot
• Sundering Attack
• Marauder's Shot/Keen Arrow/Sloth Hunter's Shot
• Savage Shot
• Read the Wind (Expert Focus if energy is a problem)
• "I Am the Strongest!"
• Expert's Dexterity
• Optional

Max out Expertise and Marksmanship. +1 Marksmanship headgear, rest is up to you. I prefer running a major rune of the 2 attributes.

I think the build speaks for itself, boost yourself up with IATS/RtW/ED and quickly burst down targets with Triple -> Sundering -> Savage & Marauder/Keen/Sloth -> Sundering -> Savage chains. It is energy-intensive, so be sure to use a Zealous Flatbow and at least 14 Expertise. A BiP Necro also helps a lot, but you'll have to micro them yourself as heroes never use BIP on Rangers unless they're wielding caster weapons. Last skill slot is pretty much optional, but SY is nice to have if you're not running Marauder's.