But the real crux of the argument is the interaction of the benefits of riptide and ES vs. Grace. Both the CH benefits of RT and H% benefits of ES lead towards the player utilizing as much of their toolkit as possible or necessary (or, even if the use of their toolkit isn't promoted it is still not restricted). Grace functions differently; it does not impact atonement, PW:S and aoe heals, which should be a huge part of disc's caliber (most of their tree is devoted to the first and second dynamics). It lends itself to paladin WotLK healing, and while it won't be quite that extreme, it suggests that interesting and fundamental nuisances within the spec could very well be ignored in preference to a blander, yet more # effective, style.
I agree.. the interaction of Grace with most of the discipline spec is negligible. Its a very direct solution to the hps issues with the class and hopefully an effective one, but arguably not the most interesting one.
I think simply letting Penance stack Evangelism on heal or damage would have been far more compelling, and contrary to complaints by noisy shaman on this thread would have required more skill, interesting decision making about when to use AA (pop AA for another heal buff and mana return during frenetic healing phases or keep Evangelism stacks up for the impending return to smite / atonement rotation to maintain high / efficient Smites.)
I understand Blizz has stated that they dont want to lock you in to using a certain spell (though they expect you to use the right tool at the right time) so they may not be in favor of putting so much weight on Penance, but it does seem to make sense as a hallmark of the Disc tree.
Anyway, I think the Grace buff will probably be tuned until launch because its the most direct and easiest solution.