What bothers me most about this is not that I won't get to play with the big boys if I want to raid 10 man, it's that there won't be anything really to aspire to except farming content after a few weeks into a tier because they've said that the new heroic mode is essentially the difficulty of the current normals. I'm not in a guild that barrels down normals in a week, but we certainly don't spend close to an entire tier clearing them. The whole time we are clearing the normals in my group, my sights are set on the heroics where I feel like the fun part begins. I understand that top guilds have this happen now- they get the heroic modes cleared in weeks and then they're just farming, but for me the content currently lasts an entire tier and trying to squeeze in as many heroics as we can before the new stuff comes out is part of the challenge.
I don't begrudge the larger raid size their fun. I'm disappointed that Blizzard has decided that to give them their fun, we have to have ours removed. I'm not really sure the game will be much fun without it.