I miss the BC attunements--I remember when my guild downed Mag (pre-cube nerf) and as soon as his body fell to the floor, a large group of us KNEW that we just got our Champion of the Naaru titles. Those were the days of exciting yelling over vent--it was a good feeling of camaraderie. When my husband and I got our Hand of A'dal titles (killing Kael and Vashj), we popped open a bottle of champagne because those two bosses were the guild destroyers in BC. The Hand of A'dal title is the only title I wear on that toon--just because when I look at it, it brings back so many memories of the Vashj coordination, the review of Kael's weapons before a pull, DPS orders, etc. It reminds me of the "you have the Core!" macro, the sporebats, and the guild trying to push Vashj through that last 500K health while dodging ooze.
It wasn't just downing the boss, it was having visual proof that you downed it. It meant you worked with a skilled group of people. It gave you some pride.
I got the Champion of the Frozen Wastes on my new main...I don't even display it. It didn't seem nearly as challenging of a title to get--the only challenge in it was finding a group to do Heroic Oculus and have them figure out how to ride a drake, get people to not stand in stuff in Naxx, and more drake riding on Maly. I guess it's because you could PuG pretty much all those fights and get the title. With the BC stuff, it was a guild achievement--you had to work as a solid team to get those titles, and maybe that's what it boils down to. BC promoted guild strengths to proceed in raids--Wrath is really just a FFA.
My .02 cents, YMMV.
TLDR: I miss the BC stuff, would love to see raid attunements again--I never got to see the class quests in Vanilla, but I would love to see more like them--maybe it would show people there's more to their class than AoE.