Ashar The Sand Mother has like 95% damage reduction???

I finally dropped a 4 trial level 77 Djinn Barya and fought my way to Ashar basically two shotting the two bosses before her (under 10 sec fights). After fighting her over 5 minutes I managed to deal 90k damage to her. It´s like she had 95% damage reduction at least. There were no modifiers that made her tankier, only one that made hear deal 30% more damage.

I was using cluster mortar cannon totems for breaking armour and then dealing damage with furious mountain + slam + walking calamity buffed by war banner. No idea what the hell happened. It´s like the attacks just went through her because I barely gained any rage.