I feel like many people are just frustrated that the game they fell in love with in BC or WotLK is not there anymore. Rather than an EXPANSION, Cata turned out to be something much different. New content and gear and all is great, but I'm frustrated that Blizzard felt the need to "fix" the game so much. I mean - you have 12 million subscribers or something, so many more than the next MMO out there, that the game is really in a class all its own.
So why change it so much?
I like the fact that healers and tanks aren't the only ones responsible for your HP and threat, but I don't think people understand this. I know some dps players play as dps precisely because the game fulfills their desire to show up, suit up, and pew pew for some good times. If they wanted more responsibility, they would play a healer or tank.
And rather than stop and approach the game and their class from the perspective of being something totally new, they become frustrated that they way they've been playing for a year suddenly doesn't work at all.
After learning how it works, I really enjoy tanking and dps. I found healing, on the other hand, more enjoyable in LK. When the dps isn't doing well, it's a frustrating nightmare that can't be handled. When the dps does well, I get bored. Throwing a "big" heal for something like 4% of a player's health just doesn't make me feel like I'm doing anything.
If I had to fix the issue, I'd try to make healing more like LK, but leave the rest the same. Let the mechanics hit really hard. Let just a few seconds in the fire mean death, but then after that mechanic is finished (fail or success), let the healer quickly return the party to max health in the fight.
For me, it has something to do with the notion that if my group took a big hit in LK, I could rock some heals with a cooldown or something and get everyone capped quickly. In Cata, I feel like, no matter what, it's going to take several seconds to heal everyone up, and I'm left wondering where all my pwn went.
I like the notion that you can't just heal through someone standing in the fire, but once they solve the mechanic and get out, don't pin all the responsibility on the healer. Maybe there could be something where taking damage from mechanics that should be avoidable cause heals to be ineffective while the player is taking the hit - only as effective as they are now. And when the player gets out of the fire (as an example), only then can the healer hit them with a big heal to cap them back off.
The real sad part here is that I see many many healers abandoning healing and really enjoying dps and tanking, learning it as a new thing, but I fear that by the time people realize that healing is more on the tank and dps than ever before, there just won't be any healers left!