Having a fantastic 4 piece bonus like that is not as great as it sounds. It is a bonus that may keep warriors in T8 gear. Magic damage reduction of that magnitude should be a baseline skill, or not in game at all. Giving it to a set bonus is not a great way to implement it.
Personally I am unhappy with the T8 bonuses and libram for pallies as well, but I think set bonuses should always be something which can get better the next tier to not keep people in lesser tiered gear.