This is a highly offensive Vladimir build with little magic resist and armor, which, you've probably already noticed. The reasons for this:

Ideally, this build will be used by someone who is in lane with a support champion who is sporting several health regen aura's but this IS NOT required. A mid or solo top Vlad can have a highly positive K/D ratio with this build.

You should very rarely stand and flat out fight before level 6. This Vlad is very weak before level 6 so you should only farm minions and poke with your Q for the most part.
The benefit is once you play very cautiously pre-level 6, you should have enough gold to get the Revolver and every AP rune is now higher than its flat AP rune counterpart at this level. Additionally, by this point the opponent thinks you are not an overtly aggressive or threatening player and their chances of overextending themselves are increased.

As Vladimir, it's easy to avoid death and stay in lane at low levels of health so you should not have to leave before level 6. QQQQQ.

Once you have reached a fair amount of health, (just completed Rabadon's) you should keep your E at 4 stacks constantly. 1) This keeps your health regen high. 2) This makes your Q more powerful 3) If a team fight breaks out, especially in lane with minions around, triggering your E at the 4th stack will hit everyone for a large amount of damage and the spell vamp will return more health to you than this ability cost.

Save pool for escaping a death or slowing an enemy who you can definitely kill.

Beginning fights with your ult is rarely a good option unless your E is already stacked. If your E isn't stacked, initiate with E, then Q, then R, only to continue chaining E first and then Q infinitely.

I'm going to address the common complaints I've heard with this build and try to explain why I feel this is a more viable buid. Also, if you have helpful advice please comment! I'm fine with getting improvements.

1) Why don't you have magic resist runes?
With running spell vamp, I discovered that having Glyphs and Marks or even just Glyphs devoted to magic resist (for a mainly mid Vlad) detracted from his survivability surprisingly. I've tinkered a lot with masteries and runes and I'm still not convinced I have the magic formula, but!, with having additional AP and the starting 9% spell vamp I have always done better with Vlad because I heal for a vast sum more.

2) Why no cool down reduction runes?
I originally did use CDR runes but as my build developed I discovered I was building items that gave AP and, nearly coincidentally, gave me CDR as well. With the 40% CDR cap, the Deathfire Grasp, Spirit Visage, and Boots of Lucidity hit the 40% perfectly without waste.

3) Late game Vlad gets destroyed without magic resist and armor/Vlad will get focused/Build Banshee's Veil, Abyssal Scepter, or Force of Nature.

With ghost and a smart, economical use of your pool combined with your spell vamp and large amount of health restored from your Q, surviving shouldn't be an issue. If you ghost, then pool, emerge from the pool and Q people while running to the nearest allied turret and still die, no banshee's veil is helping you.

Abyssal Scepter and Force of Nature are much more viable options and I think they can definitely be used. In fact, the last item in this build is the one I am hesitantly suggesting because the last item is VERY match situation based. In most games I've had with this build, I don't have an issue with survivability or getting ungodly (or godlike should I say) fed. I don't find a defensive FoN Vlad as much fun. In fact, I only have the Spirit Visage in this build because it is so great when combined with the Spell Vamp and Vlad's E.

The last item in this build is the one I am most shaky on because Vlad has so many different options to go with because of his Passive and his Ult. If the team really needs something, you can almost fit any need that that may be so the last item can change from game to game. Honestly, if you're having a problem from AD champs destroying you, keep the Hourglass. If having problems with AP champs, build an Abyssal Scepter. If you're getting the floor mopped with you because something went horribly wrong early or mid game, then by all means sell the Deathfire Grasp and substitute a Force of Nature and a Warmog's into the build somehow. If you have no problems surviving and you only need one more item to buy, go with a Void Staff. I put the Hourglass because in most non-ranked games, some AD AS/LS champ is going to be ruining everyone so the Hourglass gives armor and AP,which of course, stacks more health onto you.

The two items I recommend playing with is the Hourglass at the end, and if you find you're in a good place but could go farther or instantly need defense, sell the Deathfire Grasp and trade it for a Void Staff or a Force of Nature.