<DPS>
My opinion is DPS classes. Its the class that actually becomes "more powerful". Doing more damage is the universal measurement of strength in games such as this. But why?

Heres my analogy: Your a priest, and your in Warsong Gulch with your warrior friend. Your solo healing him and keeping him up, and he runs in and rips apart 5 people in 6 seconds. Who is truely more satisfied? The Warrior of course, its just a more satisfying thing to do.

<Tanking>
I think tanking is the second most satisfying playstyle. Its always fun to be the centre of attention, and the person who is stopping the mob from killing your fellow players. However, being a tank is pretty useless when your not raiding. Its always nice to be able to take a lot of hits, but hey, what purpose does that serve when your not tanking?

<Healing>
Ahhh, the healers, the backbone of raid groups, yet the least satisfying. While its fun to save player lives, the fun level greatly diminishes when there are 15 other people doing the same thing. Its probably the most robotic role in the game, and the role that gets the least credit. Why? Because its very difficult to express your healing skills in world of warcraft. This is because the definition of a good healer cannot be monitored properly. DPS have damage meters and aggro control, and tanks obviously hold targets. While there are healing meters, they do not express accurately the performance of a healer. However, after a long period of time, one can evaluate a healers performace, but it is still subjective.

A huge part of the fun factor and satisfaction comes from players playing well and being recognised for it. Healers unfortunately miss out on a lot of this.

We all love recieving new and more powerful loot, it improves our characters usefulness, and to some degree caters to our e-ego (pun intended).
Its a subject I think about quite often, which class is more "satisfied" with loot upgrades from raids? Who is truely rewarded? I think this goes hand in hand with the above subject. DPS become individually stronger which is the most satisfying, especially due to pvp and dueling etc, while tanks and healers get gear that helps them help the raid.

In other words, dps classes get loot that increases their characters overall "strength" (which includes raids, pvp and solo play) while tanks and healers get loot that increases their characters effectiveness in just raids/groups. It seems to be more selfless as a tank and healer.

When it comes down to it, a healer and a tanking class can only progress in their raid effectiveness, while a DPS class progresses in all aspects of the game. While healers can heal in PvP, and tanks can sometimes play a part, it is not as satisying, in my opinion, than being a DPS class.

On the other hand, playing DPS in raids is more "robotic" (to use your word) and significantly less varied than the other two styles. They need PVP to keep them from going batshit nuts, y'see. ;)

I do think your point about the satisfaction of receiving new gear is a good one. I cared significantly more about gear upgrades on my Rogue and Warlock than I've done on my healers. So, too, do raid groups at large- better-geared DPS means deader bosses!

Let me guess, you play a healer that wishes you were a DPS class?

You also assume that PvP and dueling is primary reason to get new gear, and that is what is satisfying about getting said gear. I think a lot of people would disagree with that. Furthermore, I find it pretty unsatisfying to be a DPS class in raids, because your contribution is utterly quantitative and measured constantly, not that I don't personally enjoy maximizing my DPS, but it's just sometimes utterly boring.

Try playing a DPS class for a year and realizing you have little to no control on the outcome of the fight, despite doing your job perfectly. Last night we were doing Loatheb without buffs, and getting him to 68% in 2 minutes on the dot every single pull. What was the DPS even there for except to die as healers practiced their rotation?

my primary character is clearly a DPS class, and i've played it for over a year and a half and still love it. that being said, i've both healed and tanked on my alt (lawlferaldruid) in raid situations, and i found both of them quite satisfying as well. but i enjoy trying to pick apart encounters in the broad sense, so on new content at least i'm rarely just looking at how to best shoot the big bad boss, so in that sense my enjoyment of raiding is entirely divorced from the class i play.

that being said, i think it's painfully obvious that 'what is most satisfying' depends entirely on the individual and what they enjoy. our retention rate for priests is perhaps the highest of any of our classes - 5/7 of the priests at our first rag kill 16 months ago are still playing, and 7/8 of our priests from our first nef kill are still here. they must like something about what they're doing.

I love healing in non-farm content. Knowing that if I screw up we're probably going to wipe is far more exciting than if I screw up, we might not have quite enough dps (but we probably will). Farming content is significantly less boring on a dps class, though.

Also, I certainly do gain PvP power from raiding. Going from blues to raid gear in PvP has increased my health by almost 1k, made me go from ~200 to about ~600 +healing, and given me multiple activated survivability boosters. You can't keep a warrior alive to kill five people in blues unless the five people are all terrible. I can.

Also, it really isn't that hard to tell the good healers from the bad healers. The good healers are the ones who never seem to run otu of mana and never have the people they're assigned to keep alive die without a very, very good reason. If your tanks are paying attention to who is keeping them alive, it shouldn't take them more than a few runs to figure out who they want to be healed by.

I think playing the same role for any long period of time will make that role seem boring to you.

I play a priest and love bringing my rogue to MC / BWL raids, but I know rogues / dps warriors that love bringing their priests ; )

Nothing as satisfying as a 3.5k Natures Swiftness crit heal on a MT just as he/she's about to bite the dust.

I felt a bit emasculated when I started playing my druid after so long as a hunter, but I love a lot of the healing now. It's the best feeling when you're assigned to one tank in a healer-light raid and you have to absolutely play at the edge of what you can do to keep him up.

In fact I like it so much I've just levelled a priest...

To give an example, in our guild, we have certain named people who we compliment on their ability to do huge dps, and praise named tanks for their ability to catch and hold targets. However, its very difficult to name individual healers for their healing efforts. We only know that our healing is "good enough" to do X amount of content. This is because we simply do not know which players are healing better than others. But we do know which of our tanks can hold aggro the best, which tank has the fastest reflexes, which dpser does great damage in X encounter.

Fixed.

Anyway, to the OP, I am impressed that you've managed to level and equip three different characters to have such a wealth of firsthand experience upon which to base your claims. Here's a synopsis of your post:

gurg i want to have your orc-babies.

I would think this varies from guild to guild. Our guild most definitely has a best healer, and everyone knows it.

(It isn't me :( )

Additionally, in fights/raids where one healer is assigned to keep up certain people, you can definitely see from their feedback and the healer's performance what kind of job was done. In full-crosshealing situations that's obviously harder.