1. WIP (work-in-progress) just means I haven't yet tested every piece b/c I haven't yet found every piece. So some of the listed items are based on feedback from players who have. It's also why there's an Alt setup. I've done everything except the 5 Ubers listed at the end of the End-Game section with that setup (minus Royal Circlet, Emp Glory, and BotSQ).
Bladestorm/Moonstrike = Phys/Magic. Fusillade/Wraithsword = Phys. And all your buffs are made for boosting Phys damage. But there are a lot of items now that add flat Elemental damage. And with the removal of (most) monster immunities, an Elemental setup became a viable option. You'll need decent amounts of Elemental pierce to make it effective, though.
2. More DEX = more damage, AR, block, and defense.
It's all laid out in the "How to Play" section. But to reiterate: regarding general survivability, Sorcs can't stack enough of the primary defensive mods (Life+Defense+Phys Res), so they have to layer a wider variety of defensive mods in smaller amounts. Think of it like medieval European armor. Knights didn't encase themselves in 1/2" steel. They wore thin plate over a mail hauberk over a padded gambeson.
For Life sustain specifically, you're layering regen+LoA+leech. Living Flame provides good regen and Baneblade gives enough LoA naturally. So you just need a little leech from Ber-crafted Jewels or gear to supplement those 2 sources. This (combined with other mods) allows you to handle most non-1hko situations as long as you don't stop attacking and you don't get slowed/chilled. Use Healing pots to further supplement your regen, and moon cookies In emergencies. Additionally, with a little leech, Fusillade+Living Flame can regen your entire Life globe in about a second or 2. So it works well for keeping you alive when you can't melee. And using Fusillade before a retreat can save your bacon when casters/rangers are mixed into mobs.
Edit - General guide update:
The guide should be pretty much up-to-date now.
The Valthek fight and the Uldy fight still need work (though all Yshari and Uldy stages are complete). And I'll continue testing gear as I find it and updating the Dimensional Labyrinths section as I complete more tiers.