I was originally excited when I saw this change. Finally, deciding which meta gem to use is an interesting decision, as opposed to: "this is the one and only dps meta, activate it". However I think that this missed the mark, and with such a difficult requirement it will never be activated. An interesting decision requires each option to be equally tempting.
Lets talk about some more interesting meta gem requirements:
"Requires more blue gems than yellow gems"
"Requires more yellow gems than blue gems"
"Requires atleast twice as many red gems as yellow gems"
These are requirements that would be more interesting than 'activate and forget'. They will Impact how we value gem slots on gear, and how we gem them.
At the moment I just put int+hit gems in blue slots, int+haste gems in yellow slots, and then reforge to the hit cap, knowing that the extra hit earned me more secondary stats in the reforging. This means I really don't care about the difference between yellow and blue slots, its either red, or its not.
Now imagine how any of those meta requirements would affect gear and gem selection. For example with the first one, "Requires more blue gems than yellow gems", if my gear has as many yellow sockets as blue, I might consider socketing an int+hit gem in a red socket, or gemming pure int in a blue socket, just to activate my meta. Also, it would make me value blue sockets slightly higher in gear selection.
With the third example requirement, "Requires atleast twice as many red gems as yellow gems", I would need to think twice about stacking mastery/crit/haste, it would be a natural counter balance in the game to any secondary stat becoming to powerful and being valued higher than a primary stat.
These decisions are interesting decisions that engage people when making gear decisions, it rewards intelligent gearing and gemming. Blizzard, please don't dumb it back down, you had a good idea, it just needs a little tweaking. Give us a meta requirement that makes us think, about what meta we even want to use, and what gems to socket because of it.