My guild has killed the Baradin Hold boss a couple of times now, killed Halfus and Magmaw once and has had attempts on the Omitron Defense System as well as Valiona and Theralion. So far my impressions of healing those encounters can be summed up as: when Blizzard's new healing system works as intended, it's fun. It doesn't work everywhere and maybe not even for all classes, but when it does I'm really enjoying it.
Last night we had our first Magmaw kill and afterwards I joined a Baradin Hold pug on my druid. Magmaw felt challenging to heal because OMGWTFAOE and Argaloth was made challenging by the fact that my druid's gear level is still fairly low. (I think her average ilevel is 320 or something, and she still wears a helm from ICC - I always imagine that people silently curse their luck for getting stuck with such a seemingly terribly geared healer when they inspect me.) On both encounters mana management was a big issue for me, yet I also had a lot of fun, and I've been thinking about why that is. I believe that there are mainly two reasons:
Firstly, having to manage my mana is a problem that I can approach both analytically and through experimentation. To think back to WOTLK raids for a moment, once mana ceased to be an issue, there were basically three things that could lead to a wipe from my point of view:
1. Not the healers' fault at all, a tank or dps messed up somehow and blew everyone up. Obviously that's slightly annoying, but since you want them to be patient with you when you make mistakes as well, you just grin and bear it.
2. A pretty obvious healer error, such as someone with a debuff not receiving heals even though they should have. This is relatively easy to fix because you know what to watch out for next time.
3. NEED MOAR HEALS! Those were the encounters were either the tank or the raid were taking such massive damage that even though you were already spamming all your fastest and strongest heals non-stop, people were still dying. I always found this kind of situation very frustrating because it felt like I wasn't really in control. Even though I was doing the best I could, it was somehow not enough yet, maybe because of gear, maybe because of simple RNG. Either way there was little I could do about it other than try again and pray that the tank would dodge at the right moment and I would get a crit when I needed it most.
The challenge of having to manage your mana couldn't be more different from that. I pretty much always run out of mana early when I first encounter a new boss for the first time (because I'm a bit panicky and want to keep people topped up just in case), but from then on it quickly becomes a game of trying out different spell selections: dropping a lightwell, switching Chakra states at different points, trying to let the HoT from my mastery tick a bit and so on and so forth, and with each attempt the progress I make is very visible as I last longer and people still stay alive.
In WOTLK the challenge was always more and more damage, and since I was already using my most powerful spells all the time there was no real difference in what I did until I hit a wall which I couldn't overcome, in which case I could do little to improve my performance. In Cataclysm the intended challenge is to balance my mana bar with the needs of the raid, and I always have the option to try tipping the scales one way or the other. So far this has worked well.
The other reason I like the new system is that it gives healers another way to measure their performance and feel better about themselves. Tam recently tried out paladin dps and mentioned how he liked that as dps he felt that he could always do better, whereas as a healer there is only so much healing to do and that's it: "I mean, yes, you need to measure your individual performance and all that but ultimately even if you cast nothing but greater heal and the group survives then you’ve done your job. I mean, you’ve done it really fucking badly but the point is you’ve still done it, and the only person likely to complain is a fellow healer who sees the butchery you’ve perpetrated."
That is certainly still true and I suppose healing more efficiently is still nothing more than a private little game, but at least it's a game I can measure. Healing done or healing per second are numbers that have their use, but they are very limited by how much damage is actually being taken and what your role is supposed to be, so it can be hard to feel like you've done well even if you've topped the healing metres. When mana matters again however, I can also look at overhealing numbers and feel that I've performed well if I healed a lot but still only had nine percent overheal or whatever. Once again the game encourages a balancing act instead of just trying to push as hard and fast as possible, and I find the act of trying to find that balance very fun.
If I had anything negative to say about healing the new raids it's that heavy AoE damage still seems to be running rampant, or at least it was on both Halfus and Magmaw. What this means is that while healing has become more tactical again, it hasn't necessarily become less frantic, and people can still die quite quickly if you don't hurry to top them off again as soon as you can. The only saving grace so far has been that in no encounter the massive damage seems to last forever, and if you can make it through the worst of it you'll eventually have a period of respite where you can heal people up slowly again.