Also: This is a build I made for 4v4 random arena. I tried it in 4v4 teams once, and our team got 3 victories before we got smashed (we even managed to beat an all-monk team.. that was fun).

Primary/Secondary/Attributes
N/E
Blood Magic: 12+1 (or +2, or whatever you want)
Air Magic: 5
Everything else however you want it. LOL
Equipment
I prefer to use a Bonelace Tunic, because it gives +15 armor vs. piercing attacks. Helps against those warriors since the chest is the most-often hit piece of armor (right?). Everything else is up to you.
I use a Blood recharge 20% Deadly Cesta, and a +10 energy & +30 health Grim Cesta in the offhand. I'm sure you can find better equipment.
Skillbar
1) Gale - 5e, knockdown 3 sec., exhaustion (no big deal)
2) Shadow Strike - 10e, 43 shadow dmg, if target above 50% health, also steals 43 (86 total dmg)
3) Vampiric Gaze - 10e, steal 54 health
4) Barbed Signet - 0e, sacrifice 8% health, steal 54 health
5) Soul Leech - Elite, 10e, for 10 sec. if target casts spell steal 71 health
6) Ressurection Signet
I consider the above to be the core skillset. You can mix-n-match the below, or use other skills as you see fit. The first two are what I use as of today.
7) Mark of Subversion - 10e, for 9 sec. if target casts spell on ally (includes self), spell fails and steal 81 health
8) Parasitic Bond - 5e, 20 sec. target suffers health degen of 1. Healed 90 when PB ends
9) Demonic Flesh (I used this for a while.. it helps keep you alive w/ 184 max health for 56 seconds.. time it right and you'll have around 700 health at the beginning of battle)
10) Strip Enchantment
Skills Use
1) Choose the appropriate target. If only 1 monk or 1 spellcaster on the enemy team, then that's my target. If 2 monks, then I take the monk that my other teammates are ignoring. If 3 monks, you're screwed.

2) Use gale. Let the computer handle running to the target. If you want to, you can try to time it to interrupt the enemy's spellcast. At 3 seconds of knockdown, it'll give you time to cast the next spell.
3) Immediately cast Soul Leech. For monks, I prefer to do MoS first, then Soul Leech after.
4) If the target is not a monk, you can probably withhold from using MoS. If target is a monk, then cast MoS if you didn't do it in step 3.
5) Cast Parasitic Bond. This degens the target a little, covers the Soul Leech hex, and helps keep you alive after 20 secs. or when the target dies.
6) Cast Shadow Strike, then Barbed Signet, then Vampiric Gaze in succesion. That order because BS doesn't use energy, allowing you to build it for VG. If you have more energy than my character (36), you can change the order of casting. Basically, as they are either A) killing themselves with SL or B) not doing anything at all, you will be pounding on them with 194 direct damage that heals you for 140 health at the same time!
Build Notes
~ Barbed Signet takes from or gives health to you, depending on your total health. At my current health of 551, BS takes 44 health from me and gives me 54 health back, for a net gain of 10. At 720 health, I have a net health loss of 4.
~ Enemies w/ anti-hex skills can be a problem for this build. However, if there are more than 1 spellcasters... then just target the other one.
~ As a necro, I usually find that I'm ignored very often, unless I'm the only spellcaster on the team. People will go after the Me, Mo, and Ele before they even think about me. I find that this gives me an advantage as I can quickly dispatch enemy spellcasters without too much interference. Usually, not always.
~ I have only 36 energy on my character, which is actually a PvE character. I can usually cast my entire chain without a problem, since energy regens a little as I'm casting. After my energy is used up, you have to think on your feet w/ regards to skill use.
~ I've defeated quite a few fragility/virulence builds with this build. All the better since I've already seen a drastic increase in the number of those Me/N in arena.
~ This also works fairly well against other necros. By using Gale to get SL on them first, you basically negate their own commonly used health-stealing skills. At 13 Blood Magic, they will still have a net loss of 28 with Shadow Strike, 17 net loss with Vampiric Gaze, 17 net loss with Barbed Signet, etc.
~ If you can't cast because you've been hit by another SL or a strong Backfire, then hopefully you'll have had your own SL cast before then. If not... well, it depends on the situation if you want to cast SL or other health-stealing spells. You figure it out.

~ This build isn't all that great against non-caster teams. Just your average steal-health necro.
~ Interrupters and energy drainers drive me nuts. But sometimes you can work around them. Usually helps if they turn their attention to someone else, hehe.
~ I'm really surprised that more people don't use SL. It effectively neutralizes enemy casters for 10 seconds at worst, and kills them very quickly at best. And it recharges in 15 seconds!! Amazing!
~ Life Transfer? Please. 30 second recharge?

~ I also use Gale to ease some pressure off from a warrior attacking me, or to put a stop to would-be runners and griefers. It makes me happy when I do the latter.
And that's it. It can probably be improved to fit your particular playstyle or needs.
Praise, suggestions, or just regular comments are all welcome. I'd like to know what you guys think of this build.
Larisu Bloodletter