The reasoning that GLA/PLD was supposed to be the single-target tank while the MRD/WAR was the group-target tank never made sense to me. GLA has two AoE provoke moves (Flash, War Drum). MRD loses Broad/Fullswing and has no innate radial AoEs that either don't cost 3000 TP or require a back combo, and even including all that has an 80 second cooldown. Overpower was basically it, until the godliness that was and still likely is Steel Cyclone.
ARgh sorry this isn't the thread for this.
edit: in short they probably are both good for aoe tanking, one'll do more damage to the group they're tanking, one won't have a problem holding hate, and really I'm just bitter about losing broad swing I guess![]()