Good for dungeons, can work in trials as off-tank, but not as main tank. One set I recommend is Tava's Favor, because you can proc it even in heavy on NB. A few good monster sets are Swarm Mother to pull ads and Scourge Harvester to have stronger heals in boss fights. Other good 5p dropped sets are Ebon Armory (gives health to the group), Plague Doctor (buffs your own health), Leeching Plate (heals you), Brands of Imperium (gives group shields), Akaviri Dragonguard (lowers the cost of ultimates). Try to have hands, waist, and weapons from Tava's so you can craft them in different weights for the undaunted mettle bonus, and also note that weapons and shields are harder to farm in the proper traits, so you are better off with crafted. http://elderscrollsonline.wiki.fextralife.com/All+ESO+Sets+Alphabetical

Your bars should look like this:
Front: Pierce Armor | Heroic Slash | Absorb Magic | Swallow Soul | Spiked Bone Shield || Reflect Magic or Bolstering Darkness or Replenishing Barrier (depending on fight)
Back: Inner Rage | Resolving Vigor | Leeching Strikes or Razor Caltrops | Mirage | Refreshing Path || Aggressive Warhorn

It's a mix of weapon skills, class skills, undaunted skills and alliance war skills:
Pierce Armor: this is your taunt, gives major breach & fracture (5.3K less resistance on target)
Heroic Slash: gives minor main (15% less damage done by target) and minor heroism (ultimate gain)
Absorb Magic: increases the damage you can block and decreases the block cost, also heals if you are hit by magic while it's active.
Reflect Magic: allows you to block for free for 7s and also reflects all spells to the caster during that time, absolutely necessary for some fights
http://elderscrollsonline.wiki.fextralife.com/One-Handed+and+Shield+Skills

Spiked Bone Shield: a group shield that also returns damage to attacker
Inner Rage: allows you to taunt enemies from a distance but does no debuff, also taunt them with pierce armor once they come in range
http://elderscrollsonline.wiki.fextralife.com/Undaunted+Skills

Razor Caltrops: a CC skill that slows the enemies and does damage to them
Resolving Vigor: stamina heal
Aggressive Warhorn: group buff that adds 15% to their critical damage for 9.5s and 10% to their health, stamina and magicka for 30s. Very important.
Replenishing Barrier: strong group shield, also buffs your magicka recovery while you have it slotted from line passive
http://elderscrollsonline.wiki.fextralife.com/Alliance+War+Skills

Swallow Soul: gives a bit of healing from damage done to the target, but slot it mostly for the healing received bonus
Leeching Strikes: gives 1K health back on light and heavy attacks, refunds stamina after it expires, good to have in boss fights
Mirage: gives you a 15% dodge chance (major evasion) and 1.3K spell and physical resistance (minor ward and resolve) this allows you to proc Tava's.
Refreshing Path: gives you major expedition (30% increased speed), a weak heal over time and also activates the barrier passive for 5.3K spell and physical resistance (major ward and resolve). Lasts for 13.5s with 5p heavy, and 16.5s with 7p.
Bolstering Darkness: reduces damage done to you and your allies by 30% (major protection)
http://elderscrollsonline.wiki.fextralife.com/Nightblade+Skills

Also be sure to use shield play enchantments (reduce block & bash cost) on your jewelry. Traits should be sturdy (reduce block cost) on small pieces (feet, hands, waist, shoulders) and infused on big ones (chest, legs, head, shield). If possible use tri-glyphs on those to get higher stats. Weapons should be infused, with crusher enchant on front bar and weakening one on back bar. Weave heavy and light attacks with your skills to recover stamina and proc the enchants more often. To maximize resistance every piece should be heavy, except hands which is better to have in medium and waist in light, so you get maximum undaunted mettle stat bonus. Also if you have CP invest a bit in shadow ward star to decrease block cost further. One important piece of advice is to only start farming the gear I mentioned when you reach CP160, if you haven't already. I've used a similar build a few months ago to tank dungeons including vRoM and vCoS HM and it worked well. Reflect Magic is very good against Chudan in vRoM because otherwise you get very high damage even trough block.