Allow for tank characters.
I am building an Ironbarb at the moment, trying to see how far I can push the build, especially with some of those badass Legendary affixes. It's all about party support with Ignore Pain [Mob Rule], Sprint [Forced March], Threatening Shout [Demoralize], Whirlwind [Hurricane], War Cry [Impunity] and Cleave [Reaping Swing].
I am using crafted Legendary gloves with 15.1% chance to Immobilize on hit, which is amazing for the sake of "controlling" monsters for your party's sake. Ideally, I want to find a party of ranged DPS that go mostly glass cannon and DPS everything to doom.
I've not yet been able to make any character other than Monks and Barbarians into Tanking machines, since those have an inherent 30% Damage Reduction...which is simply nuts.