Though I like the idea behind proving grounds, Cheapest WoW accounts i don´t know if it will play out as planned. In general it will work for the players which are skilled to a certain level and know how to use their toolbox AND what is inside of their toolbox.
But what about the players who don´t know their class mechanics and skills so well? f.e. i pugged ToT nhc and one of the healer was a discipline priest, that did not use spirit shell even once and after asking, he was not even aware of having it.
Here the proving grounds will not help these players, because it will mostly test numbers put out and voids avoided but not how this all was achieved.
I don´t want Proving Grounds to be easy, Buying world of warcraft account but without considering how to improve a player´s skill so he has a reasonable chance, there will be a lot of posts on the wow forum about Proving Grounds being to hard
And as it showed with the legendary quest chain and the celestial blessings, most players, especially the ones with dps classes, don´t like the idea of tanking rather hard hitting adds, either without the ability to kite them or without an assigned healer. (besides the fact that the tank and healer challenge was a cheap joke in comparison to the dps challenge)
So hopefully they don´t develop Proving grounds into a niche instead of simulating real raid/group situations
Ilvl scaling is the most important thing. Disappointed there's no tank swaps for the tank challenge and that the healing one is only 5 man, but it's a great start and the most exciting thing in WoW for me since lfr.