Is delay allowed?

[sharpMouse]

no.

Why? It doesn't break the rule "one press - one action". Any blue post about it?

* Step 2 (key up); set option to "Do not progress to the next step for 0.5 seconds"; send to leader only = /cast Devastate (or whatever spell you want)

Your step 2 is exactly like mine. It does a delay after real event. Why do you think that yours is better?

Also, splitting key event into down and up looks to be self-deception. I cannot find a bluepost now but I am pretty sure that Blizzard doesn't agree with this split. One key press is one event, with both down and up. You are not banned just because, as Lax said, multiply sendings are allowed if done at same time.