You can look on WoWWiki and find nothing in there that directly links to an entry called 'Spell Rotation', or 'Casting Rotation', but if you scroll down what they DO have, you'll see every class represented (including melee!) with an ability rotation.
If you google it, you get even more random information!
Spell Rotation, as I define it, is the rotation that you cast/use your spells/abilities to maximize your DPS/TPS/HPS in the most efficient manner possible.
Each class, indeed, each SPEC has their own spell rotation. There will be some variation in how individual people cast their spells or use their abilities. No one, afterall, is perfect. (except me, but c'mon, this isn't titled Spell Rotation and K, this is titled Spell Rotation and You)
There are websites out there that you can plug in your gear, abilities, etc, and it will tell you the optimal spell rotation to use. You can play around with it. See how it differs from what you personally use.
According to that website, with some other warlock putting up curse of elements, I should be running approximately 1300 DPS. (on raid bosses)
If I have to put up CoE, I should be pushing approximately 964 DPS.
If I ignore CoE and use CoA, I should be pushing approximately 991 DPS.
So obviously, I'm not as perfect as I thought. This is a major life changing moment here... I don't think I can continue.
Okay, all better.
But you see, what this means is that everyone can improve their spell rotation with either outside help like the website I linked, or just by knowing your abilities!
Siphon Life works BEST if you have all your affliction spells up on the target.
Improved Shadow Bolt can put a debuff on the target that increases shadow damage.
(I just learned that Immolate... doesn't change my DPS one bit if I include it or not. That tells you something! Bye bye Immolate!)
For mages, frost mages want their target to be frozen (or something!) to increase the damage of their water elemental. Fire mages want their target scorched to increase their fire damage. Arcane mages have their own particular rotation that they need to increase their arcane damage.
And I could go on and on and on. But I'm not feeling that generous today. You'll have to imagine what I'd say about rogues, shaman, shadow priests, etc.
Tanks need to generate a certain TPS to maintain aggro over their casters. Some people have macros to always have up shield block or maul/mangle, or trinket use.
Some of TPS is gear and hit rating dependent, as well, naturally, talent dependent.
Bear tanks should be mauling every chance they get. Just click it, and it'll go off when your next melee attack would be, in the mean while, mangle whenever it's up and lacerate in between.
Warriors have devastate and revenge and shield block and their own rotation. Paladins, likewise.
Roars, shouts, blessings, judgements, faeries... all of that goes into a tank's 'spell rotation'. 'Said, if you're gonna play the game, boy, ya gotta learn to play it right. You got to know when to hold 'em, know when to fold 'em, know when to walk away and know when to run.'
So true, Kenny... so true.
The three tanks need to gear up differently (obviously, since bears can't wear plate), but paladins should not be gearing up the way a warrior gears up. They generate their threat differently, they have different talents that redirect the damage incoming differently. Etc. But that has nothing to do with ability rotation and more to do with knowing what you need to gear up your tank. Nothing makes us more sad than to see a paladin trying to be a warrior.
Where we get into the fudgy part are healers. How do you calculate a spell rotation when what spell you need to cast depends on how much damage your tank is taking or the group is taking? It's a moment by moment question.
I'm talking raid boss encounters, since arguably, any trash or multiple mob encounter is going to have every class doing something different. Mages aren't going to be only IB or FB, they're going to be sheeping too, which changes their cast rotation. Etc. Etc. Blah. Blah. So, raid bosses where there's just arguably one person and DPS just have to focus on not overtaking the tank.
The different healing classes have different methods of healing, different efficiencies. A paladin should be spamming flash of light. A priest should be using mostly greater heals and renews. A shaman uses healing wave and earth shield. A druid is most effective by staying in tree form and casting regeneration, regrowth and lifebloomx3 on their target.
A priest casting flash heal is going to be less effective (albeit, faster at getting some health to the target) than a priest casting greater heal (even a downranked greater heal). A person with only 2k damage (not tank) from splash damage doesn't need a flash heal. Doesn't need a greater heal. Heal Rank 4 or Renew is more than enough to top them off. Now, again, this varies depending on what fight you're in.
For example: Nalorakk in ZA. He charges the DPS once and then goes right back to the tank. The DPS gets walloped for 2-4k. Does the group healer need to be flash healing OMG! to get them back up? ... No... a renew will work just fine or a heal rank 4. Less mana used. It doesn't get them topped off fastest, but it does what you need it to do, and a renew allows your passive mp5 to continue to keep your mana bar full.
Akil'zun in ZA requires a different method. The static charge that hits several people makes prayer of healing (especially during collapse) especially useful! (Or circle of healing if you are specced that far). And given that you can't tell where the static charge will hit or when a bird will come by and whack said DPS, that's when faster heals are probably more useful than a longer cast spell.
Now, this isn't saying that flash heal doesn't have its use.... after a roar by Nalorakk, the tank is going to be pretty low on health, so low the paladin next to you is going to be swearing up a blue streak. Flash heal to get him to a place where the paladin spamming his flash of light is enough to keep him alive while you hit him with a greater heal.
My shaman isn't high enough yet for me to comment on the healing differences between lesser healing wave versus healing wave. But to my knowledge, they're using Earth Shield to keep the tank up while their big slow heal is incoming, with a bonus from lower ranked Healing Wave's causing their big heal to be even bigger. I'm sure there are times when you need to hit the tank with a fast little heal to keep them alive long enough for a larger heal to go through. Naturally, shaman also have the nifty ability to instantly cast one of their spells.
The paladin spell of choice is flash of light. Boon says he can just cast that until the cows come home and he'll never run out of mana. Now, that's a slight fallacy... the longer the fight goes on, naturally the lower his mana will run. But for the most part.. yeah, he can chain cast flash of light for steady, fast, single target speed healing. Paladins however, do not excel with multiple healing targets.
Druids are kings of HoT's. Their most effective way of healing is tree of life form and not using their healing touch spell, but instead using their HoT's. Just stacking it and stacking it and stacking it. Not even specced resto, my druid can stack regrowth, rejuvination and lifebloomx3 and heal a nice chunk of health rather quickly. Druids also have the instant cast spell if they need to whack someone with a big Healing Touch for some super fast heal, as well as swiftmend.
So, spell rotation for healers... really depends on the fight, other healers in the raid with them, and who is taking damage from what.
I guess for healers... it's potion rotation! If it's a long fight, you pot as soon as you're down 2-4k mana. For my priest, my first 'potion' is my shadowfiend. Then two potions, then shadowfiend again.
I heart Shadowfiend.