The enmity system was balanced for level 50~60, at 75 damage was by far the best way to hold hate. People only used PLD tanks because they could survive standing in-front of the HNMs, eventually you had MNKs, WARs and SAMs tanking. As long as the NM in question doesn't have a one shot move then a DD could tank it perfectly fine. This became more and more obvious as the level cap increased, now it's at the point where any DD can cap hate in less then 30s and it's not even feasible to use PLD's to tank anymore.