1) Sw's are super viable in T4! While you'll hate running into the Melee Train, you'll love everything else about SW!
2) Everyone has their own tweaks to the build but pretty much everyone I see is specced in to get Powerful Draw (PD; Skirmish), Shadow Sting (SS; Skirmish), Glass Arrow (GA; Scout), and then either Fell the Weak (FtW; Scout) or Flanking Shot (FS; Skirmish). People still run the Festerbomb build but I'm personally not a fan of it. If you're looking for a good low-T4 Scout/Skirmish here's a decent Mastery Build:
Scout/Skirmish Build - For Tactics run: Powerful Draw, Masterful Aim, Instinctive Aim, and Enchanted Arrows; for Morales: Lileath's Forgiveness, Unshakable Focus (Never slot anything else), Instill Fear, and Hail of Doom.
3) So with a combo of Ruin/Mercenary/Annihilator Gear, Epic Weapons, and some BS Jewelry you should easily be able to Soft Cap Ballistic Skill (BS; Soft Cap is 1050), then focus on Weapon Skill (WS), and then I typically try to aim for Wounds and Toughness (Though if you're getting to a point where you think maxing your wounds is your only option then you're positioning yourself too badly).
4) Once you hit 31 and come into Tier 4 you want to get a full set of Ruin Gear (T4 PQ Set that drops from Gold Bags and then has a Fragment system in the lower bags so oyu can buy pieces) by farming some PQ's, you can almost always find a group going in LFG chat; grab two T4 Epic Quest Weapons, you can pick these up at Dwarf, Elf, and Empire Chapter 20 Camps and find the walkthroughs and rewards on the Wiki; Qhaysh Waistguard from T3 Elf ORvR Influence is the best belt you can have until you need Conquer/Dominator for set bonuses; and for Jewelry you can either take a Tome of Knowledge (ToK) Jewelry set such as the
The Winds Impervious for a little more defense or try to stack good BS Jewelry that you find/buy.
Hope this helps and if you have any more questions just ask!