The same thing happened in World of Warcraft back when Wrath of the Lich King (back in 2008) came out. Death Knights came out, and people figured out all 3 specs (Blood, Frost, Unholy) could tank or dps. (Note that Death Knights were the only class in WoW that ever could do this.) People had no idea what builds were good or bad (since WoW forced you to pick talents back then). So not only did you have folks trying out tanking...BUT you also had idiots who weren't taking the right talents. Therefore, these idiots didn't hold aggro well AND were squishy. The folks who had always been tanking were just fine, though.