I agree with the OP. Honestly I believe that shadowflame has a place for every spec, so to just narrow it down to Demo is a bit saddening. From a pvp standard, this is an invaluable skill to anyone who has faced melee.
All locs should have an AOE that does not require them to be in melee range. To require cloth-wears to be so close to the sharp pointy things is just dumb.
All locks do have that already. In PvE, Shadowflame isnt that much of a dps increase to really consider getting into melee range(unless you are demo or AoE'ing, which in case if the tank cant hold that aggro he needs to go back to tank school :p ) In an ironic twist of fate, a glyphed shadowflame is one of our biggest defenses againts sharp pointy things, lol.
Unlike many other players, I do have a bit of faith in the direction that the devs will take the game in MoP, however with Shadowflame being one of my biggest self defenses in PvP, I am anticipating what will become of our class. I am really not for a simplification of our class, which in a sense dignifies us from others. However on the flip side I am looking forward to seeing how these new skills play out for us. But I digress, I want to keep Shadowflame for all classes. Keeping it for just Demo makes me a bit sad.