FYI as well as what Oak said above the space bar will make you rise to the surface in water.
You can move/turn with ASDW, but with practice you’ll find it easier and quicker to mouse-turn: use your right mouse button to turn and hold down both buttons to move forward. You’ll be a lot more agile than using the buttons. I still use the buttons to strafe or move forward for more than a couple of steps though. But ASDW is not new, it’s been a feature of WoW from the beginning (as far as I know; I’ve only played since BC).
Alternatively, your jump and sit keybinds (space and x by default) will make you go up and down respectively while swimming or flying.
In my first years of playing, I never did much instancing, just questing. In maybe four years, I ran Gnomeregan once, and part of Zul Farrak once (I think).
What is a fun and valuable class for instancing? Not interested in tanking or healing. It seems that hunters are less than desired, though they are my favorite for solo questing. I’m thinking a dps Priest or Warlock. Yes, no, maybe so?
Joe
Pretty much any dps class can qualify as fun and valuable. If you play well, your class doesn’t really matter below raid level. Of course, if you play stupid, any class can suck and/or cause wipe after wipe. Choice comes down to what do you like to do? Melee or ranged? Sneaky/stabby or toe-to-toe brawling? Caster–big boom or slow rot or both? What off-spec things do you want to contribute? A boomkin or a shammy can drop a heal in a pinch. A ret pally or whatever the non-tank warrior specs are can off tank, or even save a wipe by tanking after the main tank dies or lags out. A rogue is pretty much always with the sneaky/stabby. Mages are pretty much always with the big boom. Locks can go boom or rot.
Also, if you can skillfully bring any kind of effective crowd control, and your instance party wants it, you can look like a pro. The late-game heroic 5-man instances are full of encounters that, if the entire group is not massively overgeared, are wipefests unless you can temporarily take one or two mobs out of the fight for about 30-60 seconds. And if you can skillfully keep CC up as long as it takes, or CC on the fly if things get all sideways unexpectedly, even more so.
Waaaaay back in the day, crowd control was very important in instancing, and a lot of old-timers learned to do it then. But CC became a complete non-issue in Wrath, for some reason, so a lot of us old-timers forgot. Cataclysm was an eye-opener, and I know that I had to relearn a lot of my old CC skills, but it’s been glorious doing so. One good CC can make the difference between win and wipe.
My priest is shadow, so I can speak to DPS priest.
It’s pretty fun, blasting the crap out of targets. The ability to do some AoE damage (mind sear, for instance) or dot up a bunch of toons is also kinda fun. But I like seeing the big numbers, like when I roll a train of Mind Spike/Mind Blast crits. My poorly geared priest is the only 85 I have that has ever hit a 50k single-shot crit.
And the instance utility of a priest can’t be underestimated. There’s emergency healing; there’s magic dispelling, which can be life-saver (and for some fight, almost necessary). There’s the ability to CC undeads, or to put Fear Ward on someone who can’t afford to be feared in a fight (like the tank; I used Fear Ward on tanks a lot in Wrath heroic instances. Otherwise the mobs would rampage through the group and smoosh clothies.)
Also, I like to think that Vampiric Embrace’s constant trickle of background healing to the entire party takes a smidge of pressure off the main healer. I don’t know if it’s true now, although I do remember in Burning Crusade that a good shadow priest hammering away at a boss along with the rest of the party made the party healer’s job just a matter of keeping the tank topped up.
There are a few utility/cute tricks. Mind control is fun, although I’ve rarely seen an instance group that wants to take advantage of it. I mentioned Shackle Undead.
Having a spare rezzer can be nice if almost everything goes wrong. (I’ve had plenty of instance runs where the healer was the only casualty of a pull. It’s good to save them a rez runback, and saves a lot of time.)
Mind Control is deeply awesome; best CC out there. I would pretty much always ask shadow priests to mind control stuff when running Cata heroics.
Warlocks are cool; if you glyph Fear (so that your feared creature just stands there instead of running around) your tanks will love you. You also have one of the two crowd control abilities that doesn’t break with area of effect damage (the other is mind control), which is handy if you have a sloppier tank.
Hunters are fine as long as you know your stuff; remember to turn Growl off on your pet and in fact you’re better off setting your pet on passive and setting up macros with your common attacks that add an “order pet to attack my target” command. And learn to aim your trap launcher and misdirect stuff to the tank.
I like shadow priests too. In addition to the CC mentioned, they also have several interrupts available which can be really handy in boss fights. Hmm, I really need to start playing my priest again.
Thanks for the comments - I’m going to try a shadow Priest, I think…
Joe
Hmm, makes me want to pull my priest off the shelf spec shadow, and see what she can do…
Bird, who is your priest? I don’t remember that one.
I could actually get into playing Kene (my priest) as DPS for a change, and not healing with him. My current shadow spec is built for PvP right now but if I have fun I could even go dual Shadow with him (pve/pvp). Maybe I’ll fool around with him tonight a bit.
Healingbird, and the names keep on coming 
Plus it wouldn’t be apt anymore. Another Elf betraying her parents wishes…so sad.
I forgot to mention interrupts. That’s also a plus.
I didn’t spec for Silence, and occasionally I regret it, but most critters aren’t immune to Psychic Scream, and even critters I wouldn’t expect to respond to fear-based attacks (undeads, I’m looking at you) will freeze in panic for Psychic Horror. The 10-second disarm in that case is just gravy.
For PvE, Glyph Scream, always. If you have to toss the phearbomb, the last thing you want is a panicked crowd running around aggroing everything in sight. (That’s another “Fuck me, I suck” moment from my Classic instancing history, btw.)
Kind of a shock at the auction house - Are stacks of light leather, linen cloth, peacebloom really so expensive? Holy Moley, Batman. No wonder low-level greens are selling for multiple gold…
Joe
It’s been that way since shortly after Cata came out. With Cata the amount of gold being thrown around is ridiculous. There are a few quests that are like, “Go listen to that guy talk and I’ll give you 16g.”
So a lot of people just assumed that everyone was now a millionaire so even the lowest level mats skyrocketed on the auction house.
Also some mats like Frostweave cloth are either pretty rare on the AH like a total of 18 pieces or a stack goes for 60-80g because hardly anyone is doing Wrath content anymore. I sometimes go farm frostweave for awhile just to sell on the AH to make some quick cash.
If we ever get Wardens as a playable class, will you make a Jailbird?
Thank you! I was going to list them but I couldn’t remember the name of “Psychic Horror.”
I took Silence because I was going for a PvP build - I had to give up something that was useful for PvE but I don’t remember what. I think if I were going to be mostly soloing content, I would keep Silence, but for instances you are probably better off giving up the third interrupt in favor of more DPS.