What kind of content do you want to tank?

When tanking 4-man content, the tank's ability to DPS and off-heal the group can make a noticeable difference. None of the bosses in all of the game's 4-man content really hit that hard.

In a 12-man trial, things do hit harder, and with so many DPS around, the tank should focus on just being a tank and not worry about contributing any DPS.

For 4-man content, I run 5H/1M/1L, 5p Kagrenac, 2p Engine Guardian, 3p Willpower jewelry, and 2p Torug's Pact swords and shields. (Sword and shield on both bars; I change between tank and DPS with just a swap of gear and bars, and so I use the same nirnhoned swords for tanking that I do for DPS dual-wield back bar.) My jewelry--I use cheap robust/healthy Willpower jewelry for tanking--has 2x magicka cost reduction and 1x spell power enchants. With this setup, I've been able to tank all the 4-man content in the game, including vICP, vWGT, vDSA, and vCoA. I can do a fair bit of DPS and off-healing (via Funnel Health and Sap Essence), and that extra DPS/healing really shines through if you're in a PUG with mediocre DPS--back when GroupDamage was working, I could see that in some of the bad Group Finder runs, I did more damage than the rest of the group combined.

For 12-man content, I'd run 5p Armor Master, 2p Lord Warden or Engine Guardian, 3p Endurance, and 2p Agility. Alternatively, since you get zero stamina regen when blocking, you could run 2p Endurance and a Master's Sword (or Maelstrom's Sword). Another option is 5p Footman instead of Endurance+Agility, but I really prefer the superior stat pools you get with the 2p bonuses from Endurance and Agility.