First, the Crown of Lucion Damage Buff stacks with a delay and even after stop casting Lightning Storm it stacks up. But that is not the main issue.
The first Lightning Storm channel benefits from the Crown of Lucion Buff, but as soon as i have 5 stacks, interrupt my Lightning Strom cast for a second and then start channeling again, or tap the LS, i dont get the damage bonus anymore, even with 5 stacks.
EDIT: Cataclysm also does not benefit from Lucion stacks, not sure if it should.