The main idea is pretty much in the title :P.
A couple self-imposed restrictions to keep in mind for this build:
1) Needs to have the Blood Ritual Passive
2) Needs to have Firebats with the Vampire Bats rune
3) Needs to be petless (I'd like to play the WD that way)
Other than those 3 points, feel free to offer suggestions on how this build could be improved. Below, I shall justify my choices:
Blood Ritual + Vampire Bats:
I love Firebats, but one thing everyone knows is that it drains your mana FAST. I'm not a huge fan of things like Gruesome Feast because I prefer total consistency over needing to rely on luck, even if the odds are fairly good (because then I'll feel bad when I get unlucky). Blood Ritual and Vampire Bats have an interesting synergy - Blood Ritual helps ease the mana drain of Vampire Bats, and the Vampire Bats' lifesteal helps offset the health cost of Blood Ritual.
I'm not sure if the lifesteal will completely offset Blood Ritual's health cost, but it can at least mitigate it. Essentially, it's almost like getting the regular un-runed Firebats, but at a 15% cheaper cost to cast :P.
Poison Dart (Splinters)
Because even with Blood Ritual and Spiritual Attunement, I'm pretty sure that Firebats is still going to drain my mana pretty quickly, and I'd need a fallback to let my mana recharge now and again during a fight. Poison Dart with the Splinters Rune is also a very nice boss-killer
Haunt (Resentful Spirit)
Although the battlenet website doesn't display it, this rune changes Haunt to deal something like 287% weapon damage over 3 seconds. That's a really powerful single-target DoT with a quick turnaround time. If there's one thing that monsters like Tomb Guardians taught me, it's that sometimes there'll be high-priority targets at the back of the enemy mob, and that often, it's more effective if you had a way to directly assault it and deal with frontline enemy minions later. This is where Haunt comes in - its role is to let me quickly eliminate high-priority targets that may be shielded by other monsters (difficult to snipe with Poison Dart). Haunt + Poison Dart also lets me kill bosses and large frontline fatties like Unburied (Firebats shines against hordes of weaker enemies, not a small pack of large, tough badguys).
Grasp of the Dead (Unbreakable Grasp)
Nice AoE snare to increase survivability (no pets, remember) and make Firebats more effective, as enemies will have an even harder time getting to you. I used to value the reduced cooldown rune more, but lately I've been seeing the value that an extra 20% slow would have, after seeing how fast certain Nightmarish monsters can move.
Spirit Walk (Healing Journey)
My panic button. Or if I just want to top up my health for free inbetween fights.
I used to take the Jaunt rune. But then I thought: "what if my spirit walk gets ended prematurely because I took a lot of damage?" Spirit Walk with Jaunt could potentially last only 1 second (don't get any Rune effect bonus), but with Healing Journey, even if your walk got ended early, at least you get a little something extra out of it. I figure it also has good synergy with Blood Rites. I'm very open to suggestion on rune choice for this skill, though.
Mass Confusion (Paranoia)
For tough fights.
Again, I'm very open to Rune choice suggestion here. I think that a lot of the runes for this skill are very effective for this build.
As for the Jungle Fortitude passive, that's just there so I'm a wee bit tougher, since I don't have any pets. I figure that I have good enough damage since I can cast Firebats for longer than other builds.