One of the nice changes in Patch 2.4 is that temporary weapon enchants fully work in feral forms. The Elemental Sharpening Stone always worked for us for an extra 1.3% crit, but it was such a pain to get that rare Molten Core pattern crafted few of us bothered. But the Adamantite Weightstone can be made by any Blacksmith and is commonly for sale for about 1g. Last an hour and persists through death, well worth the expense.
According to Toskk's DPS tool the weightstone raises my cat DPS about 3%. Most of the extra damage comes from the extra +12 damage per hit, not the crit. With our 1.0 attack speed cats benefit greatly from +damage (vs. +attack power); it's why the Crystalforged Trinket is such a great, easy-to-get trinket for kitty.
I'm less excited about weightstones for bear tanking. With the slow bear attack speed the +damage effect is only 40% as valuable, although the crit is nice. Then again it certainly can't hurt for threat.