Vazu

Let's compare two rings. Also, don't forget that nearly all of the armor rings are getting buffed. The stats on Ring of Unyielding Force are from live only. This makes the benefit even more obvious when you consider at least two physical DPS classes are assisting you.

1. Band of Dominance
Finger
+27 Stamina
Equip: Improves your resilience rating by 15.
Equip: Increases damage and healing done by magical spells and effects by up to 25.

2. Ring of Unyielding Force
Finger
200 Armor (294)
+27 Stamina (31)
Equip: Increases defense rating by 21. (22)
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Now let's compare the upsides and downsides of each on a 1:1 ratio. (The armor is what my Warlock has with and w/o)

1. 1234 Armor, 337 Resilience, 350 Defense
Armor: 10.47% mitigation
Resilience: -8.55% to be crit, -17.10% taken from crits
Defense: 4.36% dodge
Spellpower: 25

2. 1434 Armor, 322 Resilience, 358 Defense
Armor: 11.96% mitigation
Resilience: -8.17% to be crit, -16.34% taken from crits
Defense: 4.67% dodge, .32% reduction to be hit and crit
Spellpower: 0

What did you gain/lose by using the tank ring, vs. heavy physical DPS teams only?

Mitigation: Gain 1.49%
Crit % reduction: Lose .06% (Taking defense into consideration)
Crit dmg reduction: Lose .76%
Dodge: Gain .32%
Miss: Gain .32%
Spellpower: Lose 25

I'd say the choice is pretty obvious when you have 2 of anything physical assisting you. Now take the stats above, and buff the Ring of Unyielding Force as shown in the (2.1.0) indicator. Overall, the lost Spellpower is very minor. You can't DPS anything when you're dead.