Been messing around with a build centered around trail of cinders since last night. Basically, it's ****ing awesome.
The basic goal of the build is to use vault/trail of cinders to kill things, and to generate a ton of disc so that we can vault more.
Vault/Trail of Cinders
This is mandatory, and is our main damage dealer. It does absolutely absurd damage. But since it's very resource intensive, and monsters don't always stay in the cinders (thus requiring additional vaults), the rest of the build is designed around generating disc so that we can vault more.
Also mandatory. Suppression fire gives 1 disc for every mob hit by the multishot. Multishot is used primarily to generate disc, NOT deal damage, so it's useful to think of it that way. Think of your hatred as extra disc waiting to be converted with multishot. A couple mobs clumped together? Blow your hatred with multishot = full disc bulb. The extra damage is nice and multishot is useful for blowing up trash mobs (especially little fast ones), but in elite fights it's used only to generate disc.
Also mandatory. Again, disc disc disc. I've been using invigoration, but battle scars or backup plan (or even focused mind?) will work.
Shadow Power: Gloom
Not mandatory, but I certainly wouldn't want to play without it. The LoH returns from cinders are pretty weak, but with gloom up the life leach is great.
Entangling Arrow: Shock Collar
This is pretty good in 1.04. Solid damage, solid LoH, and allows us to control the mobs better which - depending on the mob type - synergizes really well with trail of cinders. More on that later.
Rain of Vengeance: Flying Strike
Free spot. To be honest, I'm not really sure what to put here. RoV is fun. Hungering arrow would be nice for single mobs, especially goblins, which are a pain to kill with this build. Bats would be more hatred, so more multishot, so more disc. Open to suggestions here.
Passives: Archery, Nighstalker/Perfectionist, Vengeance
Vengeance works really well with this build, especially if you have some pickup radius; you'll get globes frequently as you vault around. Plus it fills up your globes between fights. Plus the extra hatred means an extra multishot.
HOW IT WORKS
There's basically two different methods depending on the type of mobs we're fighting.
For anything that is willing to chase us in a straight line, let it get close and then vault away and let it chase, running through the cinders and taking massive damage. Use shock collar between vaults to slow the mobs down so they take longer to go through the cinders. Anything that's willing to chase through the cinders is going to be trivially easy to kill.
Mobs that run away are trickier, and basically involve vaulting through them to lay the cinders right under them. We vault around, lay fire everywhere, and then line the mobs up for multishot to refill the disc, then vault more. Gloom if things get hairy (using gloom and then vaulting through mobs will give massive life leach), prep if empty on disc and and hatred.
Another strategy is to simply stay at long range from the mobs and snipe them with multishot and shock collar. This is not efficient, but effective against certain types of ranged mobs if you can just dodge their projectiles.
A good mix of offensive and defensive stats is optimal. Since we'll be vaulting in and around the mobs, we will be taking hits. This is NOT a tank build, the LoH is far too low for that, but it's not a glass-cannon kiting build either. A good amount of LoH (at least 800, preferably well over 1000) is needed. Trail of cinders doesn't appear to crit, and I don't know whether it incorporates crit and/or IAS into its damage, so further testing is needed there.
ETA: Extra disc is really useful. I would suggest dual wielding crossbows, both with life on hit, and at least one with extra disc. The damage from cinders is huge, so trading some raw bow damage for extra disc is well worth it.
And that's the build.