Clemency aside (because, for some reason, that winds up being a controversial discussion), the way PLD plays completely changed in SB. Previously, outside of aoe pulls, you didn't absolutely need to use MP. Now, because of how powerful the modifier for requiescat (my new favorite word) is, holy spirit is how PLD will do a large portion of our damage and MP management to make sure that MP is there as soon as requiescat is available, is a big part of the job. Unfortunately, there's not much in game that stresses this, and frankly, one can get away with the old method of tanking. I think these people will learn in time, and the best thing any of us can do is let ignorant PLD know that way the job plays has changed.