SE never intended for tanks to use all slaying accessories in the first place and be doing like 90% of what a dps could do. That was done by players equipping str gear for their tanks. Of course we are going to see a decrease in tank damage if you use to wear all str in 3.1 but switch to vit in 3.2 there will be a decrease because of how damage modifiers work. SE is ok with this because it seemed they didn't like the high dps numbers tanks were doing in the first place due to people using str gear. SE expected tanks to be all full vit with all the fending stuff they put in the game.