Thing is, there is no equivalent mail item for the slots we'd bid on.
In a general case though, he would be right. In a situation in which progression still matters, sticking to your highest armor class is usually more beneficial for progression given a relatively well-itemized dungeon.
Now obviously if in Sunwell there are leather DPS bracers and they just completely neglected to itemize mail ones, you'd have an argument - but for the most part I do not see this happening. The leather/cloth/whatever might be better itemized in some cases, but in most cases the upgrade is not worth enough to risk wasted loot in a progression-minded situation.
As a fury warrior, a lot of 'best in slot' items for me (as far as I have calculated) are leather - Helm, Chest, bracers, Belt, but I'm never going to take them from a rogue that needs them, as there are 'almost as good' plate options available to me, that would get sharded otherwise. I'll stock up on the plate dps gear that there is little to no competition on, and then pick up the awesome leather pieces once the rogues already have them.
However, if for Enh Shaman there really are no substitutes, then I think it's fair to go for them. We have a very good Moonkin in our guild, and there are very few leather upgrades for him, he mostly just has to take cloth, and it's not really fair to deny him cloth if it denies him 90% of his upgrades.
It's similar for enhancement shaman. Other than [Midnight Chestguard] and [Cursed Vision of Sargeras] the non-set mail options are either best in slot or close enough to pass until the rogues and druids have them. I personally won't dip into leather until our rogues have what they need, although looking back I probably should have gone ahead and looted one of the early midnight chestguards, since it's essentially temporary loot for rogues and best-in-slot for me.
Today an Enh shaman wins a bid on a leather item that the rogues also need. For the next 2 months you shard an equivalent mail item in the same slot and leather in that slot doesn't drop.
Not really true at all, there are very, very few mail pieces itemized equivalent to a leather piece for an enhancement shaman (Bow-Stitched Leggings are the only true best-in slot mail items in T6 content). 90% of the mail options in BT/Hyjal are nearly a 30 EP difference from the leather options, a very significant upgrade difference. In some cases the mail items available in BT were downgrades from T5 mail items.
The other problem you also have is that it is a random loot system, everyone always says you'll end up with everything but how often have items just never dropped or only dropped rarely. A lot of times people also don't want to wait, it's instant gratification vs something that may or may not drop, and no one likes to be told they can't have something when they've put in the time to get where they are. Of course I'd like the see the loot system that doesn't see someone upset.
[Cursed Vision of Sargeras] is the prime example of this. It's best in slot for rogues/dps_war/enh_shaman/hunters/kitty_dps(?). Obviously all of those classes want it. We gave first priority to any rogues who didnt have a T6 helm. Once all rogues have T6 helm or cursed vision, then it's pretty much up for discussion between all of the classes. We use a loot council system, but on a peice of loot like this where everyone wants it we'd likely wind up having people rolloff for it. It's not a major deal by virtue of the fact that we obviously can already pass any dps benchmarks.
I think from a broader perspective, it's about maximizing your drops. You may only get 1 [random leather item] drop in 4 months, while a mail piece which is 90% as good drops a few times in that time span. If the enhancement shaman took the leather item, then the mail piece drops the next week and gets sharded and the leather piece doesn't drop again for a long time, it looks slightly foolish in the long run. You can't predict what's going to drop though, of course.
Basically Sebudai's thought process is exactly what I'd follow, and it requires you to cognizant of those other classes and what options they have.
In regards to ferals they are definitly 2nd in line after rogues for dps gear, at least for us many raids we use only 1, sometimes 2 prot warriors and then as many as three ferals at a time, and when we get to the boss don't bother to swap them out as they do more than respectable dps for us. Maybe this is easier for us because we use loot council and the only real issues we have ever had with loot were nontanks refusing to take t5 defender unless all the tanks had it, (which imo is pretty good if your biggest lot problem is people constantly wanting to pass to others.).
I probably should have gone ahead and looted one of the early midnight chestguards, since it's essentially temporary loot for rogues and best-in-slot for me.
About this, we killed Archimonde for the first time on tuesday, and a midnight chestguard dropped. We had three rogues in the raid, plus an enhancement shaman and two dps warriors. Two of the rogues rolled, and I passed since although it's best in slot for me, there are plate alternativelys and I thought it only fair to let the rogues take it first.
Then, after the raid, the rogue who won it was sorting out the gems for it, and at the moment due to our limited supply of epic gems, the guild is only handing them out for 'best in slot' items. The rogue mentioned that unfortunately the chestguard wasn't best in slot for her, because the tier6 one is better.
Is this actually the case? I guess this is a bit of a derail and may make more sense asked in the class forum, but if it's not best in slot for a rogue, then I probably will roll against them in future. As Snowy said, it's about maximising your drops, and if rogues are going to (eventually) replace their midnight chestguards, and I'm not, it makes sense for me to try to grab one quickly (I'm not sure the Rogues will see it that way though).
Rogues want to use four pieces of tier 6, so they either have to give up Midnight Chestguard or Cursed Vision of Sargeras, and Cursed Vision wins out. It's possible that when rogues upgrade either their T6 legs, gloves or shoulders in the sunwell(thus losing the set bonus) they will want to temporarily swap their T6 BP out for Midnight Chestguard. Either way, it's not best in slot for them. It's best in slot for enhancement shaman by a huge margin(55+ EP higher than T6.)
My self-inposed rule as Enhance in the t6 instances was that I never asked for the first of any 1 contested drop. This does not sound like a big sacrifice but it goes a long way with the pure classes who take particular pride in getting 1st drops.
These problems are somewhat temporary. Before long there are so many pieces dropping that the bigger challenge is finding people who would actually pick up the drops as opposed to having members squabble over them.
Some people seem to be losing the focus of the question. Rogues get priority, and there's nothing else to that. If a leather item drops that a rogue wants, they get it.
The question is what about after that. The sole discussion is between a pure DPS class/spec that can wear mail (Shamans and Hunters) should get a leather item before a feral druid who is there to tank, and it's just an added bonus that they can dps when they're not needed to tank.
In my case, the cursed vision is about 24 DPS upgrade, the next best thing is 2-4 DPS upgrade at best.
Sure, leather items that we take (like Don Alejandro's Money Belt, which is the only other leather item I want) might not drop for a while, but Rogues will already have them. It's then us, and feral druids who tank for the majority of the time and very rarely do comparable DPS when they do go full out.
Sure, a Feral having good DPS kit does nothing but help on a boss fight, but what if the MT dies? They're in DPS kit, they can't pick the boss up, so we wipe. Not only that, because of the DPS difference, even if both groups are going full out DPS, any upgrade for a Shaman or Hunter is 2 or 3 times the same upgrade for a Druid.
It's as close to being a predetermined loot system as you can get without being one, but I just see it the same as a protection warrior wanting DPS plate items for when they aren't tanking. Druids do more DPS, but it's still far, far below that of a pure DPSer.
Some people seem to be losing the focus of the question. Rogues get priority, and there's nothing else to that. If a leather item drops that a rogue wants, they get it
I didn't read that as the focus of the original question at all.
Maybe my guild is a little different, but we use open dkp bidding, with the only restriction being that the item does make sense for the people bidding to have (ie it will be used in a raid). For example early on we had a resto shaman bidding on a first drop of leather melee dps chest (after collecting elemental gear as his backup spec). He is no longer with us.
We only have 34 total raiders, so it is prudent for our multi-role classes to be able to swap roles or specs depending upon who is on for that raid. It is also our 90%+ attendance people that have multiple roles. This means that retribution and protection paladins are free to bid on healing gear, our warriors bid on both tanking and dps gear, shamans have dps and healing gear, etc.
If you are using a dkp system, you aren't going for maximum raid output. If people like using a dkp system, you will only piss them off if you change to loot council in the middle of things. Progression will take a little longer with dkp, but it can be more fun, depending upon the kind of people you have in your raid.
Edit: I probably wasn't clear enough in my original reply, but quite often you will see this in raid chat when an item comes up for bid: "XXXXitem is the best thing by a huge margin for an XXXXclass , so please keep that in mind with your bids." It is amazing what a little courtesy can achieve.