I guess I would say that based on our progression so far things like these are not near as impactful as they are made to seem.
You're damn right, it's not huge by any means. But why would anyone in a mythic raiding guild not seek to max themselves in every way possible (within reason, not everyone likes to blow 40-90k on BMAH gear) while in progression? It'd be a different story if we were 10/10M and in farm mode, but we're not and we probably won't be before 6.2 releases.
I'd argue that with 6.2, the runes go from being a bonus to practically being a +50 enchant of your primary stat, if it's going to be in the game in a form that you'll always be able to use it regardless of the AH market. And at that point, do you really want to be the guy that says "nah, fuck being always maxed because I can't grind a bit every now and then
in an MMO"?
Obviously we would never *require* people to get something like this (especially given how awful Blizz's approach to reps has been with WoD), but frankly unless you're buying the single-use runes already, you're a bit of a douche for not working every now and then toward buying the permanent one.