I don't have a problem with a system that rewards people for gearing themselves up outside of raids, but it's fairly hard to quantify in the way that you're wanting to see it done. Loot Council is the only way, and those are very subjective.
Now, there are plenty of systems that reward you for gearing yourself up in a more passive manner, like DKP. If you don't need to spend DKP on epic sword/board/chest/gloves/pants/wrist/belt because you've run tons of Heroics, then you will end up with much more DKP than someone who showed up to raid in blues, because you won't be spening DKP on any of those items. So over time (but in fairly short order if the DKP system works well), you will have a serious advantage over those who geared up less pre-raid.
Suicide Kings would produce a similar, but less pronounced effect.
/roll is totally FTL because it incentivizes people not to gear up. /roll fails as a system because loot is scarce, but the resource that buys loot is infinite (just tossing out a /roll). DKP, Suicide Kings etc. limit one's opportunities to get loot, which incentivizes people both to gear up outside of raids and to make smart decisions about whether they really need an epic that drops during a raid.
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