Many of the old builds still hold true. Three things I would recommend having somewhere in your build are; siphoning attacks, a shadow ability (the armor buff), and an aoe snare (lotus fan and calthrops work for this.)

I have a magicka nb tank, and my (very biased) opinion is that magicka nightblades are the best tanks.

I have a very offensive tank spec. 5H/1M/1L. 5p Kagrenac, 2p Engine Guardian, 3p Willpower, 2p Torug. Sword-and-board on both bars. With purple food buffs, I have 31K magicka, 25K health, and 17K stamina. Buffed up, I have 32.7K spell resist (near cap), but less physical resist (I need to check, but I think it was under 25K). And 2048 unbuffed spell damage.

I change my bars around a lot depending on the fight, but I use the following skills:

1. Funnel Health: My main single-target spam. And I do spam it a lot. (Funnel is better than Swallow Soul, since you can off-heal your group and take pressure off of your healer.)
2. Sap Essence: My main AoE spam. And I do it spam it a lot.
3. Structured Entropy: For ranged boss fights where I don't need an AoE, I slot this instead of Sap Essence for getting my spell power buff.
4. Caltrops: Good way to grab initial agro of a large group, esp. when combined with Sap Essence, and a great way to proc Siphoning Attacks.
5. Siphoning Attacks: Always keep this up for the resource management.
6. Double Take: For the Major Evasion buff.
7. Summon Shades: A low-cost shadow ability that I cast to proc the Shadow Barrier resistance buff. Also debuffs enemy damage (I don't use Low Slash) and adds a little to my DPS.
8. Pierce Armor: Melee taunt (my preferred taunt, since it debuffs resist)
9. Undaunted taunt + Mark Target: I slot these on my bar for purely ranged fights (e.g., vFG or vDSC final bosses) for ranged taunting and resist debuffing. I usually don't have them on my bar. I don't bother morphing the Undaunted taunt.
10. Defensive Posture: I don't cast this skill (so I left it unmorphed). I slot it on my front bar purely for the passive bonus from slotting it.
11. Harness Magicka: For fights where there is a lot of spell damage and not a lot of stuff to block, I use this instead of Defensive Posture. (e.g., Engine Guardian, Ash Titan, Mola Kena, Maw of the Inferno, etc.)
12. Impale: Execute.
13. For ultimates, I use Veil of Blades, Ice Comet, and Barrier, depending on what the situation calls for.

It's a very active and offensive tank that can pump out a lot of damage--and I have to: my self-healing is based on the damage that I do, and my procs of Siphoning Attacks (to keep my stamina bar filled for blocking) require that I constantly be casting Funnel or Sap.