Highly contested items can be decided easily but first picking one of each class, for the token that then leaves you 3 options or less - usually resulting in a /roll for classes who all have the same level of previous item.

I'm assuming that you only let people pick up these off-spec items after all of those players who use those items as their main-spec have picked them up or have no longer have interest in the item? And that you use the normal DKP priority for who has first choice on these off-spec items, i.e. DPS plate drops, 2 tanking warriors present interested, top DKP holding tank warrior gets first dibs on it for the zero price of the weighted % price. If any of this is wrong so far be curious to know what you do for these situations.

Ok, now for the real issues. It seems that this is a good solution for items like DPS plate or moonkin gear when there is really only one class that would want the item. However, I think problems might occur when dealing with items that multiple classes would be interested in. Now still assuming what I said above, if say a caster DPS ring dropped, you might have Healing Priests, Healing/Feral Druids, Holy Paladins (or would you not consider them in the off-spec category for this), Prot/Ret Paladins, and Enh/Resto Shamans.

Now let's just say that there hasn't been much Feral Druid loot and Feral Druids are the highest in priority out of all these groups. They would then have first dibs on this DPS Caster Ring, and it wouldn't change their loot priority (stop me here if I'm wrong). However, most would probably agree that this item would be more useful to the Healing Priest, Resto Druid, Resto Shaman, or even Holy Paladin to be used for solo content since the stats have better synergy with their main spec. The Feral Druid is going to just put it in his bank for that time he might spec Moonkin (at least that's where all my moonkin gear has gone and rarely ever come out).

Also, I want to add in the concerns my guild has had with this off-spec gear issue. Basically the argument is that off-spec PvP gear is held in high value for those who like to PvP. They also want to help the raid succeed and get the PvE gear, but they don't want that to set them back from getting the PvP items they place higher value on. A big complaint in starting up new DKP for the expansion was seeing a loot sequence of Tank Plate to Warrior A, Tank Plate to Warrior B, Rare Uber Weapon or DPS Plate to Warrior C. The situation with off-spec or PvP items is rough and the fact that some classes have to deal with multiple gear sets while others do not will always be a problem with any loot system as you have stated. It's hard to reward those that are getting the PvE gear the guild needs them to get while still keeping an even distribution of loot. It's hard to give someone Tank Plate & DPS Plate before another person gets any items. I think your idea will solve the problem for a lot of the armor over the long run, and that's a good improvement.

I think with all systems you're going to have to rely on your players to not have the druid take an item he may one day use in moonkin form, over the dps caster. Thats really kinda assumed - even with full purchases, only that point cost will prevent them. As Zwink mentioned, you just have to control the offspec overspending. We always just naturally have the gear go to the classes that see the direct benefit first.
As I did mention though, 0 point pricing would be competitive, and no it wouldn't change their priority. Not really an easy solution, but this was also part of the idea of splitting the cost over multiple items, that total a fixed amount.

This is exactly the situation I saw with my previous guild's loot system, except that other factors compounded to make it impossible to even change loot priority. As a zero sum fixed price system ages over time, you'll find that the average DKP level of long time raiders raises well above zero. This is because trials who don't make it pay points and leave in the negatives, thereby increasing the standing of all people who were present when they did loot items. The same thing occurs when someone plans on leaving the guild, spending themselves into the hole. After two years, our loot priority ranking almost perfectly correlated with the duration someone had been a member of the guild and changing position was virtually impossible.

When that guild reformed, they did a revamp of the loot system since they saw the issues at least with their implementation of zero sum DKP. I won't repost my entire essay on the subject, but the core of issue came down to this:

Rare Loot vs. Common Loot

All loot fits into one of two categories, rare or common. Loot that drops often enough that everyone who wants it will get it in a reasonable amount of time is common. Loot that doesn't is rare. In general this means that stuff like Rejuvenating Gem is rare and T2 Bracers are common. Given a 10% drop rate on the gem per clear, getting 15 gems for 15 healers in a BWL raid will take almost 3 years. Two bracers per week from Razergore means your raid all gets outfitted in 20 weeks, or 4.5 months. The former is not a practical goal while the latter is. Not to mention that having a variety of other bracer upgrades means not everyone will want their T2 bracers, but a dearth of healer trinkets means all healers want the gem. A lack of suitable alternatives will make an item rare enough that not everyone who wants it can get it.

In some sense, the common items aren't worth worrying about-- everyone will get them in the long run. The fairness of a loot system is measured in its ability to distribute rare loot. Suppose raider A has double the attendance of raider B. The system is fair if A gets twice as many rare drops as B. What I've seen in a priority based loot system is that A gets all the rare loot and B gets none. If three rare pieces drop, A shouldn't get all 3. They should get 2 and B should get 1.

But to echo what Gurgthock said, it's easier to tear down than build up, and I concede that other systems have other issues.

I just don't see that using DKP in TBC solves more problems than it creates.

As Gurgthock has already stated: There's just not that many approriate places for any given peices of loot in a TBC raid to go.

And a bit of common sense can be used to handle most of the problematic "rarer" items that have a broader appeal - stuff like trinkets that may appeal to warriors, rogues, hunters and feral druids.

The decay system makes it more likely that new players will enter at the current average point holding, but it's not sufficient to guarantee a good distribution of players looting rare items. My old guild had something similar to decay, where people with more DKP paid more points for items. The problem is that the optimal of an item is not based on stat increase alone, but also the difficulty of obtaining a similar stat increase for that slot from another item.

Suppose you get the same stat increase from either Ring of the Martyr or your T2.5 shoulders. Most guilds would give these items the same price. The problem is that looting your shoulders generally drops you low enough on points that you won't be able to get Ring of the Martyr again (because who knows when it will drop), but the reverse is not true. You can loot the ring, go lower on points, and just grab the shoulders when everyone else has their stuff.

This is essentially the example Gurgthock had of three rogues in 5/8 nightslayers and barman shanker but one rogue in blues and a perdition's blade. And it's worth noting that technically the problem isn't even the priority based system (although that contributes). It's pricing that only takes stats into account, not rate of item supply. To me, rarity of drops is the hardest part of determining a fair price for an item. You can't determine the value of an item from the stats alone.

If I had the means to design software for handling zero-sum DKP, I'd include a feature that would, when you flagged a player Inactive, immediately, retroactively, and dynamically go back and discount them from the point calculations for any raids in which they participated, both removing points earned by them and divvying them up among the other attendees, and removing any points awarded for items purchased by them.

The system would thus remain perpetually truly zero-sum with respect to all active raiders.

And if the inactive guy came back you could just toggle him back to Active and it'd recalculate everything.

Right, this is also a big part of it for us. We have a smaller, higher-attendance raiding core than we did pre-TBC, which simplifies these issues. When you have 7 players of class X rotating through 3 slots evenly, I agree that you definitely need a more elaborate system to ensure fairness.

Yeah, obviously dkp systems are guild specific. Ours is pretty tight knit - but I do want those who have nothing to gain by coming to a particular instance some form of reward there for showing up later, and a trackable one - so we'll probably stick to DKP. I've also been a part of some relatively tight knit loot councils in the past, and it was fairly unnerving at times; as it felt as if favorites were played, especially with veterans. (Again apologies for the judicious use of the term loot council, but when the highly competitive items do drop, decisions will have to be made).

There is certainly an extremely strong case for loot council in BC, we all see how the distribution goes. There are just issues that I can't look past with it; just as you clearly see issues with zero sum that you moved past in BC. It comes down to what works for you.

In the end I kind I'm glad I posted this as the system vodka uses seems fairly apt for where we're at now, and simplifies things... sorta.

I just periodically rebalance to 0 with uniform subtraction. I actually used to have the spreadsheet automatically enforce a 0-balance, and it would auto-adjust anytime I flagged somebody as "inactive," but that confused people too much.

Thats part of the problem with councils though - because it isn't out there for all to see, people will sometimes assume certain items are being given unfairly, even if they are not - and even in tight groups this can play out... competitiveness of the item changes your mileage on this. The problem is the perfect loot system doesn't exist - basically due to the human element.