Our guild uses Item Levels and Slot Constants for determining item value.
What this does is put the value of
all same-Tier armor class-sets at the exact same value. For example, Druid Bracers will cost the same exact amount as Warrior / Mage / Paladin / etc Bracers. The same applies to every other piece of class-set armor of the same slot and equal tier. Once you move up a tier, then the Item Level will scale the value accordingly.
We zero-sum, too, but we zero-sum at the end of the week. This makes it so that the entire raiding week is worth about the same amount of points. For example the beginning of the week is trivial because it is Molten Core for us. We get tons of drops during MC because we can clear it. The end of the week if Blackwing Lair, which is troublesome for us (we've only been able to defeat Razorgore). BWL is considered "non-trivial" and those days are "learning days." By zero-summing the DKP over the span of the week, we're able to award people for any amount of raiding they've done over the course of the week. There are no "DKP whoring" days where people scram to get in for boss kills because they want DKP.
It's an interesting system.