As you have noticed, we will receive a big bunch of really powerful epics with Patch 2.4, and some people have raised their voices and said that all their hard work then is for nothing.
As a semi-active raider and GM of a guild that is on Vashj at the moment, I can sympathise with that, and it does seem to make the effort we have put in to be made redundant, we could just have waited. Still, WoW raiding life is a big pie-eating competition where the price is more pie, so if you don't like pie, you should probably reconsider your gaming style.
I don't have the time to go in to details here, on why I think that Blizzard is doing the right thing (but couldn't they at least have done the gear into T5 instead?! sorry, that's my selfish voice talking again...), but then I came across this post on file front. It basically says much of what I think myself:
Let¡¯s say you hand me a list of guilds that play regularly on my server. With a small margin for error, I have a decent idea of the progression level of most of those guilds. I know that the Alliance side of my server has a number of MH/BT guilds, including 2 of the top guilds in the US. I also know that we have a few guilds on Horde side working on Black Temple as well. After this patch, I will still know who those guilds are, and what they accomplished. I will still know that Risen cleared Black Temple first on our server (Even if they are Alliance, you still have to respect that). No matter what my guild, or any other guild does after this patch, what came before still remains.
So, if you are feeling blue about having "less worth" epics, go check it out, it might give you some comfort. And remember, you got to like pie to be in pie-eating contests...