I've been mulling over this particular mini-drama ever since I won my Black Heart on Darkker, much to the consternation of the tank I'd been running with. (And before the tanks out there get pitchforks, know that normal ToC is so popular among tanks it's one of the few instances where you can queue as both tank and dps and actually wind up as dps.)
I often queue as tank and dps on both my druids, and usually I end up as a tank; very rarely as dps though it's not unheard of. It doesn't bother me that I end up doing 5-mans more often in my off-spec than my main. Particularly on Hana, even her off-spec is geared enough for chain pulling. Besides, the queues are nice, and I can look at it as doing my part to help more instance runs get going.
But it's not immediately clear what my main spec is to the random pugger. Or, for that matter, what I queued as. (Which is why the Black Heart was a point of contention.)
Normal ToC I had to queue specifically for. You can't get it from the random heroic. I queued for normal ToC on my feral because I wanted the Black Heart, and being that I wanted in faster, I queued for both tank and dps. When I first did that I expected to go as tank to be honest, but it ended up being that about half the time I ran normal ToC I went as dps. Tanks love this place, and only one tank can go at a time.
So I went in, we did well, and the Black Heart dropped. I immediately rolled Need for it. My roll for it was the first one that showed for all purples in the chat log. There was no waiting until the last minute to ninja-roll. I was pretty upfront about it, and no one said anything for several seconds, which is when the tank failed to win the roll. I'd gotten the heart.
Then the party immediately said that what I'd done was not cool, that I shouldn't have queued as dps to roll on a tanking trinket. I explained that I do both and queued as both. In retrospect I could have said something at the start of the instance like "I'm here for the Black Heart. If you don't like it, leave and I'll switch over to my tank spec and we'll requeue for another dps," but I hadn't thought it would be a big deal.
One thing I've noticed is that the rules of needing and greeding have changed a lot since the cross-server Dungeon Finder went into place. If you don't Need, even for your off-spec, there's a good chance you'll be looking at a shard. One run I went on with my paladin I discovered the paladin tank was main-spec holy off-spec prot, just like mine, and he needed on everything. I passed on all the prot gear (not realizing it was the other paladin's off-spec and we had identical off-specs), but the other paladin continued to roll on all the healing gear.
The end result was the tank getting both the new 5-man tanking weapons (we did back-to-back PoS and HoR runs) because I kept passing. He didn't really need two weapons for his off-set, and he got a new healing ring too.
Now was he wrong for doing this? When I found out and brought it up his guildie told me "if you need, you need, even if it's not your main spec." He wasn't being mean. He was just being frank, in a "hey it's no big deal, need if you need" sort of manner.
And that appears to be the rule now. Most of the heroics I go on have behaved this way. Tanks roll on dps trinkets, dps on tanking plate, and so on. There's no discussion about main specs vs. off-specs. And in a way it makes sense, because people can legitimately be specced for both.
Having gone through this environment multiple times, was it any wonder that when the Black Heart dropped I hit Need?
I think for a random heroic, where it's quite clear that a dps ended up there via random selection (from their debuff), they should pass on tank and healing gear unless the tank or healer does not need. It might not be happening in practice, but I think someone willing to wait as a dps for a random dungeon is pretty solidly dps with little intention of tanking/healing and should leave the gear to those who would use it for their role. If the dps is a tank that's taking a break because they're burned out on tanking they probably have everything they need from 5-man heroics. (And if they didn't, they would have queued specifically for the instance they needed and not as a random.)
It might be a bit of a bias, but I don't think it would be wrong for the reverse to happen though, for a tank or healer to roll on dps gear, if it's for their main spec. If I wasn't willing to tank on my off-spec that would mean one more dps sitting in queue and three dps that would have to wait longer for a tank. Each dps who can tank or heal but doesn't is potentially increasing the dps queue by four.
Since the queues are longer for dps, I think tanks and healers who pug in their off-specs are doing a service by allowing queues to move faster (more runs for pure dps means more chances at gear), and they shouldn't be penalized from rolling on gear that would help their main specs.
For specifically queued instances though, people should be able to roll on what they came for, because it's more likely they'll end up in an off-spec role (or off-spec for what they want to roll on). One normal ToC run I did actually had three tanks in it, as I found out when we requeued to replace a dps. The prot paladin queued as only tank, my feral queued as tank/dps, and the holy paladin queued as tank/heals.
Arguably the run would not have happened without any of us, so I would think all three of us would have had legitimate reason to roll on the Black Heart had it dropped. We each took a different role, whatever it took to get the job done, and had circumstances been different any of us could have ended up the tank, but two of us didn't and performed the role given us. If the healer and I had queued as tank-only to ensure we showed up as a tank (as the complaining party said I should have done) we would probably have added to the glut of tanks and worsened the queue times for that particular instance.
I wonder if it would help if the Dungeon Finder would list the other roles the other players signed up for but did not get to play as. That way if someone signed up as tank/dps everyone would understand that yes he has a dps spec, he probably uses it regularly (or would like to use it regularly), and if someone signs up as just dps they can be prodded to wait until after a tank or healer has a chance at a piece of gear.
It also might clear up that ToC/Black Heart nonsense. People might fault a dps for rolling on tank gear, but they probably won't fault the tank the Dungeon Finder assigned as dps.