There are sadly many issues for feral druids.. Not suprisingly though, as druids have to be handled special. IMBA is also just as screwed.
1. All the stats shown below are in caster form, which is kinda irrelevant for a bear tank or a cat DPS'er.
2. As said earlier, the Idol of Terror is the best tanking idol still if you prioritize survival over threat generation. In my experience, threat generation is not currently what is creating problems, so I prioritize survival.
3. Enchants have totally different values for druid tanks. For instance, my +18 stamina enchant on chest is worth 5 points here. But with druid scaling that is +50% stamina in bear form (with hotw), +6% stats from SotF, and +10% stats if you have kings, which I normally have. Thus 18 stamina gives me 315 life. But if I had use the +200 or +275 life enchants I'd score 12 or 15 points even though I got much less life out of it. +10 to all stats is of course very nice, but for survival we only need stamina and agility, and since we scale so well with stamina, +18 stamina is not necessarily worse. (though probably a bit worse once you have gotten lots of stamina already)
4. Similar to the above issue, various items are wildly different for druid tanking even though they both have only melee DPS stats. Scores will vary a lot based on how much you rate threat versus survival for instance. And for survival stats, the worth of stats differs considerably from what they are worth on blizzards armor budget, which is represented by the epicness and item level of the item.
I guess it's hard to try to make up a generic rating of all stats for each given spec that most people can agree on though. But that would be very nice if one should be able to compare scores with other people.