Yeah, it was surprising to see the sale not really posted as sale in IS. Better for them if they post it as sale. That's what people look for when they open the IS.
And while people do not always regularly read, if they are posted, sale notices, they do tend to open up the item shop to see what is on sale. If they want to temporarily change the prices for those sale items in the regular area, I'm all for it, but they should still have the sale appear as a sale in the item shop. It simply is better for the company if people are easily able to see what is on sale. Yeah, it was surprising to see the sale not really posted as sale in IS. Better for them if they post it as sale. That's what people look for when they open the IS.
I personally prefer it this way. This ensures players don't buy the runes at the regular price. The old way they did it they had the same item in the IS at two different prices. That and the change was mentioned if you read the main website.
"The Weekend offer takes place between Friday the 12/09/2014 at 1pm PDT and Monday the 15/09/2014 at 5pm PDT and can be found in the Item Shop under ‘Runes’"
for sure they might need a small tweak in price. 
Nobody wants the kind of 'kiss up' that I can clearly see you detest
I believe Cike has mentioned this several times.
I personally never contemplated anything above the 600 diamonds per, which I haven't implemented. Maybe at a future time and gradually.
You were prompted to look at higher level runes because you saw others with them. And your assessment was dead on. The gain was very minimal for the amount of diamonds needed. I suspect if you hadn't seen others with those runes, you would have still been pleased with the level your runes were at. On some things, it's just impossible to compete with those who are willing to spend anything. And in this area, I simply agree with your assessment that the gain just simply isn't worth it. it's not really the price of the runes that is daunting. My opinion.
It's what some people will spend on the game that is.

Nobody wants the kind of 'kiss up' that I can clearly see you detest