I feel Demo, those players who run Demo, are fighting a battle on multiple fronts.
First off we have the UVLS nerf, yeah less proc rate that sucks but we can deal with it if need be.
Next we have the hit to Imps, 30% away from a 1/3 of our dmg, anyone with alittle knowledge of math can tell you they hit us for 1/9th of our dmg
Finally, any lock that did not play Demo pre ToT are feeling the hurt of Fury Starvation because they may not know how to conserve fury, a tad spoiled from the set bonuses from T15
yes they nerfed Demo, Yes it is worse off now, but I feel the third reason is playing a bigger part of the problem then people realize, Even I a demo lock since ICC couldnt tell what the issue was right away before finally noticing I was running myself dry on fury with no procs, I feel with a bit of work you can pull good numbers still as a demo lock.
Though like it has been stated in this thread, Playing Aff or Destro is considerably less work then Demo for the same result, so it turns into a play smarter not harder dilemma.