So I've healed HoS and HoL and I feel that when your tank has 3x the health you do, it's ok to dps. Why? Because it gets boring really fast. But at least we only wiped once. Lightning to the healer + poorly timed lag = bad bad thing.
In my Naxx and heroics I run. As a healer I would often pull whatever group I can get to, even if we aren't remotely finished with mobs we're currently on. People that come with me often down groups in a hurry when they realize that their healer isn't there.... and is probably down the hall pulling groups and running back.
Groups moving, worrying about repair bills, and down trash faster = more enjoyable time in boring content.
Downed XT on hard mode on monday. And started an alt 10 man ulduar group, downed the first 3 bosses in quest items and some 10 man pieces!
Healing, on the other hand, is less about preparation (although it is definitely important for coping with spike damage!) and more about cleaning up the mess when the other two roles do something stupid. Hence how much gear a healer needs at the minimum is often directly related to how good his teammates are.
I agree that Healing is an art, BUT
Reactive healing will lead to a lot of dead raid members. This is why Shaman and Pallys struggle in current hard-mode content. It all comes down to coping with AoE damage, which in Ulduar is... insane? Not Sunwell era raid wide AoE damage insane, but incredibly frustrating as a shaman because everyone is so spread out. Druids and Priests have the ability to be mobile and AoE heal the raid instantly. Shaman and Paladins have 1 instant on a long cooldown that is both expensive and has little effective healing.
This is why Omen is a great healer utility, because you can see a dps who might pull aggro and be ready to attempt to save them. This is why instant cast Aoe healing and absorb shields are so effective in Ulduar if you use them at the correct times rather then just spamming. This is why they nerfed mana regeneration of replenishment and will yet again nerf healer regen. This is why... ect ect ect.
As mentioned, I recently did XT-Hardmode which is quite simple in terms of execution, but the raid damage every minute is almost unbearable when you are partnered with a shaman. I'm in the group of Sixthy, the greatest shaman in the world, and have to agree that current content should be Lesser Healing Wave spam. But why should I be pigeon hole'd into a 1.2 Second cast, int or spell power stacking, and spot healing low members in the raid for REAL healers to actually top off. Why can't I assist raid damage with chain heal?
3 reasons.
1) Cast time is too long, by the time we get it off priests and druids will have taken care of it. Thus we end up over healing.
2) Heals for too little compared to other AoE that costs much less in terms of mana per health.
3) Chain heal doesn't jump nearly far enough to hit 4 people.
Healing is become a lot less about how intuitive you are or how well you can read a fight, but more your ability to roll a druid or a priest. Next patch Pallys get some love with the Beacon change. Still Shaman are gonna be sitting on the bench when it comes to hard-mode content, which really is all that matters since the normal content is so easy for the casuals.