There is no RAW ruling that would indicate one way or the other. You can't just state "by RAW" when there is nothing to read on the subject, since RAW literally means "read as written."
Rules As Written, yes. And, as written, the rules make no allowance for
allowing a hostile power to hit you, no matter the source.
So, your argument is that it shouldn't be allowed, because once per encounter it's actually useful?? That sounds extraordinarily misguided at best. You help one ally with positioning in exchange for screwing them out of most of their actions on their next turn. Sounds pretty fair to me.
It depends on what you believe I'm saying should be disallowed. Using the power on an ally is totally allowed. Willingly being hit by an attack power has no rules basis at all. According to the rules, the
only way to hit with an attack is to make an attack roll and meet or exceed the defense. There is no other way.
If you're DMing, you can rule it however you want. But I have to respectfully disagree, simply on the grounds that previous editions allowed for willingly taking attacks from allies without being forced to lower their defenses for all enemies. The ally in question already has to lose most of their actions during their next turn for taking this shot; making them a sitting target for every enemy in the area on top of it is just overkill.
I am having trouble finding this rule in the D20 SRD. Can you point it out for me? Also, if my talking about a cleric hitting himself with the power is a "strawman argument," then so is this. The discussion is about Fourth Edition--not any previous edition of the game.
In any case, my idea for lowering defenses willingly until end of your next turn comes from considering how that would have to come about. On an attack targeting AC or Reflex, the target would have to stop moving enough to allow an attack to hit. By doing that, he's not fully defending against any other attacks because he has to make sure the attack in question hits him. An attack against Will would mean that the person lowers defenses in his mind so the attack can go through, and anyone could take advantage of that. Fortitude cannot really be willingly reduced, as it is purely a function of someone's natural hardiness.
Even so, I firmly believe that no one should ever
want to be hit with anything labeled an attack, no matter the source. It just doesn't make sense, despite whatever possible benefit might be gained.