It's on/off mitigation that takes no skill to exploit and puts a negligible amount of extra pressure on healers when it's off. I feel like arguing that it makes tanks "boring to play" is grasping. Turning off your tank stance after a single threat combo isn't the "lynch-pin" of Tank gameplay; it's efficient use of your damage mitigation CDs and support skills while contributing as much damage as possible and positioning the boss/enemies in a way that allows the rest of the group to maximize their own damage/avoid damage.

I believe that the choice between mitigation/damage/threat should be resolved through CDs and rotational choices. I feel like there's room for allowing for a higher skill ceiling balancing a Tank's options between performing an enmity combo, dps combo, and balancing a mitigation combo vs mitigation oGCDs in place of simply "Grab enmity in tank stance, do your dps rotation and press mit oGCDs in dps stance"