As of last night I have now performed as a tank, healer, and dps on every fight in ICC, all on the same class. I can't think that's something common. And honestly it's not something I set out to do.
I started ICC as a moonkin with a bear offspec that I used once in a while, but not very often. Our tanks have good attendance and we had other people with backup tank specs. Our roster at the start of ICC hadn't stabilized but the content wasn't punch-you-in-the-face hard so when we needed a third healer I usually brought in my paladin, despite the fact we already had a paladin healer.
But by the time we killed the Lich King and started hard modes, our roster was stable and we had a spiffy ret pally with a decent tanking offset. It was decided that what we really needed was a backup healer, so I changed my off-spec to resto, and I healed for many a hard mode if one of our healers was missing. I also healed the normal modes of the bosses we couldn't kill on heroic yet. I even did embarrassing things like heal in my moonkin gear because I forgot to swap gearsets. (Did that twice on normal Lich King and once on heroic BQL. We lived.)
Then our ret paladin retired, and a few weeks later our OT was going to be gone for a weekend, so I specced back to bear and tanked for a couple nights.
Since our healer attendance was good I left my bear spec up since I prefer tanking random heroics as a bear to healing them as a tree. I figured I'd just go back to tree when needed. And then last night we ran into a problem on heroic Sindragosa.
We were making fantastic progress, and got within 300k of killing her (so sad!) when our MT's internet gave out. He popped on, he popped off. He couldn't stay connected for more than a few minutes, and Sindy's not exactly a short fight. We only had a half hour left to our raid night and our only backup raider online was our unproven ret pally replacement, currently on trial with our guild. He'd never killed Sindragosa before, not even on normal. Heroic was out of the question.
We made the call to switch to finish the lockout on normal. I would OT and our usual OT would MT. (Two bear tanks. Such fun!)
Sindragosa went down easily enough on normal. It was a little sloppy, but that was because our healers decided to try two healing it for fun.
Then there was the Lich King.
When I play as my off-spec, whether it's as a healer or tank, I always try to fill in the role of the missing person. For something like BQL, where each raider in the guild has a usual spot to stand, I stand in the spot of the healer I'm replacing. It means no one else will have to adjust to accommodate someone being missing. For something like Putridice that means I will be the abom if our DK is missing or the Putricide tank if our bear is missing. It means I have to be flexible, but it also means that I really get to see the different sides of a fight.
Since our DK was the one who couldn't stay online that meant I had Shambling Horror and Raging Spirits duty. And I'd have to say that I'm really envious of our DK's ability to Death Grip the horrors to himself. I hit the first one with FF as soon as I could target it only to find out that it doesn't establish a threat table right away so I had to wait a second to taunt it. I was also terrified that a dps would pull a horror off of me since our more zealous squishies have made the occasional "oops, pulled threat" mistake while our DK was tanking. I consider myself a competent tank, but I can't help feeling a bit nervous stepping into someone else's shoes, because I want my substitution to be as seamless as possible.
We did have one wipe, which was totally random (the healer in charge of cleansing forgot to dispel off the MT going into Phase 2, and that was really unusual of him), but we downed him in short order. The new ret pally won some brownie points for being excellent about Defile, considering that he'd never done the LK fight before. It's really hard to find someone who can play and won't flag as having 25-man experience on GuildOx, so I'm hoping he works out.
Being able to say I've tanked/healed/dps-ed every fight in ICC, probably gives me some perspective. I do know that if I am to set up an alt/non-raider run for the guild (it's been brought up a couple times) that I will want to tank if we cannot get a guildie to do it. But I don't think tanking is the hardest role.
The thing is… once I know what to do as a tank, I might be a bit nervous, but I know what to do. The boss's attacks don't change. Damage is generally predictable. I pot. I use cooldowns. I tell someone when to taunt. The raid depends on a tank knowing what s/he's doing, but once the tank has that knowledge and is capable of executing it, the role of tanking itself is more routine. For an alt run that may include puggers I would want to tank instead of a stranger because I trust myself more than a tank I've never met.
The role that stresses the heck out of me is really being a healer. It might be because of my lack of experience (I only went tree once we started ICC hard modes), but healing hard modes always leaves me feeling like I'm running on a treadmill with a nasty set of spikes behind me. I toss my Rejuvs and my Wildgrowths, the occasional Lifebloom or Nourish, I'll top the meters on heroic Festergut and BQL, but even if everyone lives at the end of the night I'm still wondering if I'm doing it wrong. Perhaps the whole idea of blanketing the raid with hots just doesn't work for me because it's just a tick over time, whereas I'm comfortable with the machine gun style of paladin healing because you know pretty quick whether or not you're "doing it wrong." (Tank death will do that.)
While I hesitate to say that dps is the least stressful job (being ranged dps on heroic Blood Princes will quickly disabuse any notion of facerolling), it's a job I know very well. I can feel like I'm at the peak of my performance and still have the mental bandwidth to call out instructions during raid. Granted, I can usually do the same as a tank (if I don't have boss crotch blocking my view), but I have difficulty functioning as a raid leader if I'm healing a heroic mode. I'm very much a fan of audio alerts because if I'm healing I might not see what's happening around me, but if I can hear there's a good chance I'll react.
Still, there's a part of me that finds it fun being able to fit in wherever the raid needs me. I'd rather dps of course (I love being a boomer and booming is what I do best), but I like the challenge of being able to do whatever's necessary to get the job done. It's something that probably wouldn't have happened back in my 25-man guild, at least not without a lot of consternation, but being a druid in a 10-man there's a real opportunity as a fuzzy swiss army knife.