My reservations about the system is that it rewards those that can sit and raid constantly (those without a life so to speak). So those with work and families take longer to get the same loot.
This is true to a point of absolute time spent in an instance versus relative time spent. It doesn't matter what instance you name, the more time you spend in it, you will receive more loot from it. If you spend 1,000 hours in Maraudon, you will have more loot from Maraudon then somebody who has spent 5 hours. But relatively, each person will receive the same amount per hour spent in Maraudon.
If the "loot" allocation system is designed in such a way that everybody can expect to win a drop every 9 hours in an end game instance reset then it doesn't matter if you have a life or no life. Every 9 hours you spend in ZG means you can expect to take something away. If you have enough time to spend 18 hours a month, then you can expect to be taking 2 items. If you can run it for 180 hours, then you might win 20 items.
There is also the concept of diminishing returns. In Maruadon, the princess drops two really nice caster items, a crown and a necklace. As a priest, if I have them both already, other casters will have a better chance of getting loot from a princess run then myself because they will not be competing with me on those items. Same with end game instances. If you just started running MC with ONE, you might only be competing with 1 other warrior for the Bracers of Might because all the other warriors already have them or have better.
There are also other limiting factors on a DKP system. Such as a 1 item limit per run. So even if somebody has hoarded 5,000 points, they will not take away all the drops. Once they get their item, they won't be bidding on any other items that run. People who are hoarding are usually doing so for a very specific drop. So, if in a run, all the priests except yourself are hoarding points on the hopes the priest epic staff quest drops, they will be passing on the prophecy items that drop. Meaning a pickup, or a priest that doesn't run often will pickup those peices.
As for what items are used to increase DKP: Often events that anybody can achieve are a good starting point. Showing up on time for a raid, staying a full raid, being on for 75% of the raid duration as an alt, taking down bosses are all events that no matter what guild you are from as a pickup will gain you points. How you gain points should be fair to everybody and transperant. If we pickup somebody who runs with us 80% of the time, they should be able to gain points at the same rate as somebody in the guild who also runs 80% of the time. Adding in events that people outside of the guild can't take advantage of will slowly leave them alienated which will in turn cause a decrease of good will with our guild in the community.
IF WE COULD RUN ZG guild only (which we can not at this time) adding in events or items such as steping up and taking a leadership role in the guild (helping out, running a bible study, showing up for one etc) we could incorporate that.
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There are other systems other then DKP. There are modified roll system. For example, your /rand 1-100 will increase by points for showing up on time for raids etc..etc.. Lets say over a few run you've gained 60 points. Your random roll would be /rand 61-160. If gives you a better chance of winning an item over somebody who has only 20 points (21-120) or just started (1-100). Somebody who just started though, still has a chance to win (they could roll a 98 while the person who has 20 points rolls a 42 and the person who has 60 points rolls a 75).. If you win, you loose all your bonus points (back to 1-100) and when combined with a 1 item per instance reset rule, you won't be rolling on any items until the next instance reset.
Under a modified\weighted roll system, if you don't win anything, after a short while you will get your self into a near gauranteed win position (ie...rolling 101-200 versus people rolling 1-100). But never really removes the chance to win something every run or every other run.
The items\events that add to the bonus on a roll should be available to everybody on the raid and transperent. If we could run ZG all guild only, we could add other modifiers. And even if we had to pickup some people, they would be able to roll on loot right away (1-100) instead of waiting for DKP to be added up.