Today my friends we learn what to do when you're dpsing. A lot of people playing any class miss the boat here, you can have all the purples you want with a sweet spec, but if you don't know what to cast when you may get a message from Ferth with tips on how to increase your dps.
Your spell rotation depends on your gear, your spec and what you are dpsing. I'm going to assume you have both gale winds and eclipse in your spec. I see these as must have talents if you plan to do heroics/raiding as balance. Also I'm going to bank on you having the Glyph of Moonfire and Glyph of Starfire, I can only think of mean things to say about someone who would be running with anything different.
First we have the wonderful world of trash mobs. This is pretty simple, when there are multiple mobs use hurricane. Gale winds makes a huge difference in dps here. The faster your group kills trash the better and most of the time there are to be 3+ mobs in a pull. Hurricane and /lol at Bluetide. Not really, that would be rude. In the rare event that you get one trash mob it depends on the hit points it has and the dps of your buddies. Go with a moonfire, starfire until eclipse procs then wrath if it's going to take a while. For things that die quick it doesn't really matter, spam wrath works for me.
Working with Eclipse there are different procs based on what rotation you use. I prefer to use starfire to proc. I like to keep rng out of my dps as much as possible, which is why I don't like this talent. The 20% damage on wrath is on every cast (that doesn't miss). It's possible to have your chance to crit with starfire increased by 30% and never crit.
My rotation for bosses is moonfire, starfire until eclipse procs then wrath until the proc is over. This is where it gets fun, and by fun I mean irritating. Eclipse can proc then you get stunned, or the boss can't dpsed or someone need to be decursed or moonfire is falling off. If you are unlucky you can cast 10 starfires and not crit, which kills you mana and is bad for your dps. What you do when eclipse is up is a big part of your dps. Whether you should cast moonfire depends on how much longer eclipse is up when it wears off. It is almost over 2 or 3 seconds just keep spamming wrath otherwise reapply it. Once eclipse is over then starfire and reapply moonfire until it procs again.
In a prefect world bosses would just stand there and let you just stand there and cast until it dies. Most bosses aren't so kind. If you need to dps a single add that dies quickly spam wrath, it it takes a while to kill use a normal rotation. Hurricane if there lots of adds, Starfall is nice here too. I don't use insect swarm at this point, without the glyph it isn't a good idea. Unless you are one those wonderful bosses where movement is required. If you have to move cast it and if moonfire is on its last few tick reapply that as well.
A few other things, make sure treants are up on cooldown (on bosses where they are usable) and make sure heroism/bloodlust is cast when they are up. Also use on use trinkets during this as well (heroism, not treants). If you have Starfall it does a good amount of dps for one gcd. Another thing, don't stand in fire, red or black circles or blizzards. Moving lowers dps, but not as much as dying.
On healing, if you are brought as dps, dps. Unless the raid leader asks you to start healing or you need to heal yourself, don't do it. If all the healers are dead I think your safe to start healing with out being told to. Your healers should be able to handle it, you don't see feral druids who are dpsing switching to bear and taunting because the tank is getting low do you? No, that wouldn't be good.