I was trying to think of a tank that would benefit the whole trial group... so I came up with this:

Argonian MagicTemplar

5pc Ebon armor (chest, waist, hands, legs, boots)- increases group health by 1118
5pc Worm (ring, ring, neck, sword, shield)- reduces group magicka costs by 5%
2pc Lord Warden (medium armor)- summons shadow orb to raise physical and spell resistance to nearby allies by 3870

Tank bar:
Backlash - Pierce Armor - Restoration Focus- Radiant Aura - Ritual of Retribution ULT: Aggressive Warhorn

DPS bar:
Radiant Oppression - Puncturing Sweeps - Inner Light - Structured Entropy - Explosive Charge ULT: Meteor

This should be especially effective when the new patch releases... considering that Argonians will get 9% increase to healing done. So, with Restoration Focus active, Ritual of Retribution should be doing some decent damage while healing anyone near the boss.

Edited to replace the Ultimate. Warhorn vice Nova.