The way I see it.. the benefits of landing all 4 EM+CL -exactly- the same time (minimize healer reaction time) are miniscule compared to the benefits of landing them in succession over roughly 0.3-0.5 seconds.

It has 2 major advantages that I find non-trivial:
  • Unforeseen last split second grounding totems eat only 1 or 2 of your nukes, vastly increasing your chance to kill.
  • Warrior spell reflects reflect only 1 or 2 of your nukes. This also increases chance to kill.
Some people will probably argue that this is neglible, that I need to learn how to read the opponents. However, there is so much stuff to pay attention to in a 5v5 battle, that I just don't have the mental capacity to count the seconds since the enemy shaman last dropped his grounding, or to notice that a warrior has equipped a shield. I'm usually very busy keeping myself alive in matches against real teams, so when I do decide to go for a nuke, I can't spend too much time thinking about counters.