Ok, I'll try to give you a simple explanation about it.
First of all, I really LOVE Poison Dart "Splinters" rune, but, 60% slow is indeed really a helping hand both against white mobs and elites and it has saved my life countless times already. I'm playing alone on Act 1, most of my time, and i'm trying to make some serious gold before venturing fourth. For that reason I think numbing darts really help me, even though the dps is really weak, the slow here is awesome. But, if you're playing with friends or someone who can actually tank some elites for you, I highly recommend Splinters.
I must say I didnt like haunt very much before lvl 60 but now I think it's really a great skill since you can cast multiple times and you have high mobility AND damage. I also choose slow for this one for obvious reasons... I don't know the math but, 30% plus 60% from Darts is a really nice slow, even though I know its not 90%, its great, the only flaw to this combo are super duper fast elites like spiders, frogs and these "magekillers".
Do I really need to talk about Spirit Walk? I guess not... Right?
Soul Harvest is great since it can be used as some kind of a potion, or maybe even better, and a dps booster.
Now, we reached the thing. Wall of Zombies Dead Rush is an amazing skill, especially when u are surrounded. Although it has a high cd (25 sec) u can do A LOT of dmg if you hit 2 zombies on the same mob/elite. I'm not really well geared yet, I have 24k Hp and about 30k DPS WITH 5 stacks of Soul Harvest, u know, nothing really off the chart. Normally I hit elites for 65~70k with this skil, almost the same with zombie bears critting, but when this skill crits, its like 100~120k dmg. AWESOME!
I think horrify is an excellent skill to have in ur arsenal, maybe even better than Mass Confusion due to its low cd. Normally I use it as an escape skill, to make me free from mobs gaining some move speed in the process, you know, more like a panic button.
I guess Pierce the Veil and Spirit Vessel are kindof irreplaceable passive skills. I use Jungle Fortitude cause I don't have a nice HP and my resistances are all still low, something like 200~250, so I can't afford taking a lot of hits, so any kind of defense is welcome. If I had an ok Hp and high res, I would replace it by Blood Ritual, Spiritual Attunement or Rush of Essence, so I could spam Haunt even more, or maybe changing Horrify to a more offensive skill, maybe bats. Anyways, you can try some variations and see if it works!
I have no Idea if this build works beyond Act 1, so if someone could try it and tell me how it was, it would be really great!
So, my rotation is something like this:
Haunt 2 or 3 mobs
Wait for them to get close OR run TO them with Spirit Walk, Soul Harvest at least 3 of them and then Zombie Wall Dead Rush on them aiming for the strongest possible (if its an elite). Its important to be well positioned to use this skill, so you can hit 2 zombies on the same enemy.
Back up a little bit while still on Spirit Walk and attack with darts hit-and-run style
If u get surrounded or held/teleported at use Horrify to make them go away and use the bonus MS to reposition urself.
So that's basically it!
Thank you for reading and I'm awaiting for some replies!
I like that this build is using a skill I've never found much use for (+1 for inventiveness!). However, I see some holes that may need filling.
The way I see it, this build is a CC/Darts build with pizazz. All the slows make it really nice to kite with, but mobs that are resistant to slows (I.E. naturally fast mobs like fallen, or Fast typed elites) will be a REAL headache. There isn't enough CC in here to reliably deal with them either, so they will be a major problem for this build. Since this isn't a tanky build, getting anywhere near enemies (esp. in A2+) is a definite bad. Having two abilities that require you to be reasonably close (Soul Harvest and Zombie Nova) seems odd since this is a kiting build at heart. 445% Weapon Damage is an impressive number, especially if you are going glass cannon style, but in order to use the Zombie Nova you are basically having to sacrifice yourself unless you plan to immediately SWTFO.
Two ways I can see to address these issues:
1. Since this is a build based around not getting hit (Slows and kiting), I would suggest swapping out Dead Rush for maybe Pile On. You get that godly amount of burst damage, but it is a little safer because you won't have to deal with being so close (still pretty close, but better). This change may bring up an issue with dealing with AoE, but Pile On doe have a decent area it hits if I'm not mistaken.
2. If you REALLY wanna keep Dead Rush, then consider making this into a tanky build. Grab a shield, tons of resist all and health, and maybe add Dead Rush as a variation to one of the skills described in other tanky builds (such as this build from the official forums that I have been using for a while now). It may add some badly needed oomph to an otherwise "steel noodle" build.
I have never really thought to use dead rushdue to the Cool down time but I could imagine replacing my fetish army with the ambush rune for it instead...Specifically in group play, going in with spirit walk, laying down a BBV Slam dance while getting a 5 stack soul harvest potentially picking up some health globes for Gruesome feast and letting one of these off would be a considerable amount of damage. Especially considering you could get easily use this ability several times during the course of a boss fight. Solo play I would prefer popping fetish army as they make great distractions and let you unload your darts for a siginfigant amount of time.
Also I would like to add Kiting would be very difficult with out grasp of the dead, you do get great slow from haunt and snake to the face, but.. in diablo everything comes in waves of monsters and very rarely 2-4 monsters, I have experimented using grasp of the dead and haunt with slow rune kiting champion packs and it is very effective but you are dropping a skill for that single target slowing DPS not to mention it is very expensive if you do not have proper mana regen, again possibly dropping another passive to support it.
Spirit walk with jaunt is extremely effective at getting you in and out of a mob quickly. your movement speed is GREATLY increased and your path of travel is completely un obstructed. using jaunt I can come from across screen, drop a BBV, soul Harvest, fetish army, grab health globes and relocate to a tactical position before it wears off. So getting close to mobs isnt really a huge problem when spirit walked.