Shroud of Saints in effect does this. The healer dumps half their aggro instantly and very quickly the tank can easily regain the aggro lead on any/all mobs pon the healer simply by using their normal aggro maintenance skills. The net effect is that the healer shed aggro to the tank.
I've seen healers pull a pack and bring them bak to the tank expecting the tak to take them, and popping shroud of saints just as they arrive at thet tank. The net effect is exactly what you describe. Oh, and while we're talking about someone using sprint, I consider the fact that DoM players have no penalty for sprinting to be a clear lack of balance. Sprinting does not in any way affect the ability of DoM to do their job, while Sprinting cripples any DoM, especially Paladin. A Paladin has to manage their TP, HP and MP, all but one of our primary battle skills consume TP, and other skills (including Flash) consume large quantities of MP.WHM sprints ahead in a dungeon, body aggros a bunch of mobs, uses assize and maybe a swiftcast-ed medica II, then transfers the aggro to you?
That's really not at all an equivalent situation to allowing PLD to possibly execute a battle-raise, or for that matter use Clemency and Divine Veil. Those are all situational skills, and frankly, even with battle raise capability, the 8-second cast time and large MP consumption make the use of Raise extremely situational.It's your responsibility to use skills AoE threat skills. Would this be okay? Healers occasionally being able to take care of your AoE threat for you?
Your example has the healer intentionally sprinting ahead and proactively face-pulling mobs. That's literally usurping the primary role of the tank. Situational 'healing' skills such as Clemency, Divine Veil and (assuming we had it) battle raise do not even remotely tread on the primary role of a healer. Even if you can propose theoretical situations where 1 PLD can save a wipe by using HG, and raising a healer, it can easily be countered by pointing out that the same PLD would be better popping the LB before everyone falls, or if the healer sees the wipe coming, they pop their LB and all is well again. Those well neglected tank and healer limit breaks are there for a reason, it's just that the community has fixated on burning bosses making the LB mandatory for finishing the boss, or a phase.