Either:
-5x Hist Bark: Craftable, good for starting tanks and tanks who block in long durations without healing support (there are situations like this)
-5x Ebon: Giving 1k max health to your entire team has a pretty noticeable effect in trials, make sure you or the off-tank uses this set somewhere in their build.
-5x Torugs Pact: Increases the effectiveness of your Crusher enchant, allowing you to give your trial groups better optimized damage.
-5x Plague Doctor: Massive stack of health. If you really need to focus on survival, particularly in a place like Halls of Fabrication and Asylum Sanctorium, this is a good set for giving you some serious health bonuses.
-5x Dragonguard: Reduced Ulti Cost. A strong all rounded set.
-5x Resilient Yokeda: When you are tanking enemies away from the group (vSO is a good example), this set can really do some good things for you.

-2x Blood Spawn: Provides random hits of resistances and ultimate on 2pc passive over time when you take damage, both really useful.
-2x Lord Warden: When you run with a team of 4 Warhorns Lord Warden will give more utility to your team than Blood Spawn, which is what you want.
-2x Mighty Chudans: I know, I know, why would you run Chudans? Well, just watch Woeler's explanation on tanking Monster sets for this update and why Chudans is a good choice.

-5x Alkosh: Unparalleled in terms team support, the 5pc passive removes both physical and spell resist from the target, allowing you to achieve full armor penetration on targets affected by the shockwave. Don't run anything else if you have a full set of Alkosh, things die really quickly when this set is applied.
-5x Bloodthorn's Touch: A great starting option and much better than Alkosh if you are tanking enemies away from the group without support.
-5x Werewolf's Hide: Similar to Bloodthorn, good starting option and great for solo tanking. A lot more expensive to get a hold of in Jewellery+Weapon form though, so just be aware of that.