the argument that no caster should be able to cast and move may sound logical and fair on a general level
However, if you understand affliction spec, you realize that removing KJC at its current state and leaving rest of Affliction unchanged will actually make Affliction unplayable and broken.
If Blizz wants to change KJC mechanics, thats fine, However they need to revamp the affliction spec altogether in terms of DOT damage numbers, Fel Flame Mechanics, haunt mechanic and Shard procs.
Bottom line is, if they want to increase the skill cap of affliction by tweaking KJC, that's fine. As long as the rest of the Aff spec is re-balanced as well so that a good player can still pump out decent DPS.
What wont be fine, is if they change KJC alone and end up breaking affliction completely.