Back in my low 60s Cheesi and I were constantly running the early TBC five-mans. During this time, we happened upon a Druid about our level named Nitedragon. We pugged with him several times and developed a good relationship, and he was kind enough to give healing a go so that we would have an easier time putting groups together.
Soon thereafter, Nite joined our guild. He immediately became one of the most helpful, willing, committed guildies we had.
When we started the TBC raiding game, Nite, much like he did when we were running Ramps over and over, left his comfort zone to meet our needs. Our guild suddenly had healers, but the only tanks we had were me and about 25 Hunter pets.
Nite specced Feral and went off to do his homework. He figured out how to spec, how to gear, and worked very, very hard learning how to tank. When we hit Kara, we hit it hard, and Nite and I ran through that place side by side week after week after week. We jokingly referred to him as "Mis's pet bear."
With all the research and all the practice, Nite got good...very good. He bailed me out when I picked up adds, grabbed bosses if I died, executed perfect chain-pulling, and prevented many wipes with quick-thinking and flawless tanking.
Our first time in ZA, he and I nailed the tank-swap and one-shot Nalorakk without breaking a sweat. He once picked up Nightbane after I dropped and tanked him through to the kill.
Now, when we run Heroics together and he comes along in cat form, if I overpull there's instantly a very large, angry bear standing next to me picking up the adds. When we ran Naxx last weekend, he did a lot of great work snagging adds and protecting healers and let me focus on bosses...many of whom I had never seen before and most of whom we one-shot.
So why am I gushing about Nite?
Because the guy has turned off-tanking into an art form. It's not like a lot of runs I've been in, especially pugs, where the guy with the lower gear score automatically gets put on off-tank duty. Instead, Nite recognizes it as a distinct role...different from that of the main tank and equally, if not more, important.
While I'm locked in on a boss, Nite is often running around grabbing adds, protecting healers and overzealous DPS, and making sure that he's always ready to charge in and pick up the boss if I die. He constantly has a ton on his plate, but he makes it look easy and actually enjoys it.
What can you take from this?
If you're an off-tank in your guild, don't feel like you're less of a tank than the main tank. That doesn't have to be the case at all. Off-tanking is a different job than main tanking...if you approach it that way and take the opportunity to learn to do it well, you'll be helping out your raid group immensely.
If you come across a good off-tank, not just one who facerolls through the boss fight while thinking about what tank gear that boss drops, show him or her a little love. It takes a special kind of person to take on that much responsibility and not care about who's getting the glory.