Shamans have always been a great class to play, whether it was in classic and you spammed Chain Heal in ZG or BC where you did the same thing in a different zone. Well the zones weren't all that different but that is a conversation for a another time. And in WotLK, Chain Heal spam is still prevalent, but it is mixed in with so many other powerful spells it isn't mindless. With riptide, Tidal waves, and even Lesser/Healing Wave shamans have a variety(though not as large as priests) of spells to use. However, unlike some classes, shamans spell are extremely straightforward.
Take paladins for example, I had no idea what Beacon actually did until a few days ago. Now maybe I'm just stupid but it honestly confused me. Even priests, with nearly ten spells to choose from at any given time would confuse and annoy me. The way shamans heal is by large direct heals that can be spread out over large distances. I could possibly have Riptide rolling on four people at a time, and with the improved distance Chain Heal jumps I can sometimes hit ranged when the melee was my target. It is, in my opinion, still the paladin that will come out on top in fights with minimal raid/large tank damage, and holy priests with the opposite. Shamans, however, can compete with the best of them.
Take ToC 25m. Many of the fights in it have AoE damage, well all of them do to varying degrees but it is in the high AoE fights that a shaman will excel. Take the Twins fight for example, a fight easily lost if people don't pay attention. I can hit over 5-5.5k hps on this fight. Granted so can druids and even priests if they are holy, but it used to be that shamans were brought for Heroism/Bloodlust and whatever else they brought was just extra. With high mana regeneration rates as well, a shaman is one of the longest lasting healers as well.
As I've been tooting my own horn this whole time, I'd like to point out something I dislike about shamans. It seems to me, that a shaman is much less dependent on gear that other classes. I'm not even close to being as geared as our main pally healer, yet I can easily beat him on many fights. Our heals scale with gear more than is fair to other classes.
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