As Destro/Demono hybrid, I wonder if I should use spell stone or fire stone.
Of course, should be fire stone but i read 2-3 times that spell stone > fire, even in destro/demo...
Spellstone if i recon.
Edit; EJ says it should be a spellstone, However.. The lock guide here says the firestone would be better because if you get too much haste you might clip your spells @ heroism/BL.
Its most likely a personal preference.. I'd stick with a spellstone unless you get close to clipping your spells, At that point, go for the firestone.
Especially if you are going to try to stay conflag after the nerf, the 1% increased dot damage helps buff conflags damage. Weighting stats wise, haste is stronger then crit, and the amount of haste on spellstones is higher then the crit on firestones. Spellstone tends to be a clear winner here, although it will take some more getting used to for soul fire weaving, especially under the effects of heroism.