Druids can reach the armor cap against a boss-level enemy with current itemization:

Item Armor
Pillar of Ferocity 550
Thunderheart Harness 3152
Thoriumweave Cloak 390
Umberhowl's Collar 281
Belt of Natural Power 423
Treads of the Den Mother 516
Violet Signet of the Great Protector 392
A'dal's Signet of Defense 367
Badge of Tenacity 308
Mark of Tyranny 180

This adds up to 6559 armor from items. The Druid's Dire Bear Form armor bonus, combined with the feral Thick Hide talent, gives a druid 550% of the base gear armor. This would result in 36075 armor, just over the 35880 needed to hit 75% reduction against a boss (This does not include any bonuses from Agility or enchants/armor kits).

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