This build focuses on making [Frost Prime] have maximum mitigation.

Armor is also a primary contributor to Snow Globe health.

Elemental Ward opens a whole new buff, the main bonus is 150% armor which equals +450 flat armor in addition to the above.

Based on the conversion of armor and power strength, a single stack of Snow Globe with Elemental Ward up should be ~25k without Arcane [Guardian] or other party buffs which means a 100k health snow globe.

With conditionals and Elemental Ward, DR will approach 90%. Recommend a Heavy Attack melee weapon for maximum tank utilizing [Carnis Carapace].

If you can't do an Umbra Forma you can alternatively drop [Armored Agility] and equip a Carapace which is one level below max. This means you require one less regular forma as well! Still 9k EHP with 83% DR

Alternative Aura mod would be [Combat Discipline] if focus is group support, benefit is it will also proc Arcanes.