This tends to drift into the old D&D problem of "if it has stats I can kill it!" Just because the rules allow for you to be throwing 8, 9, or 10 shifts of power into your aggressive evocations, why are you, especially around mortals? Harry is in the top 20 or so wizards when it comes to raw power, often has a bit of fallout when it comes to his big spells due to his lack of control. Why is every Tom, Dick and, uh, Melvin throwing around Senior Council worthy evocations all the time. It strikes me that those big spells should be saved for situations that call for really big spells and dramatic effects.
Just my thoughts on the story-based issue involved.
Thoughts for keeping it in line:
Especially for White Council characters who intended to play it straight. Invoke and compel those aspects against them. Using lethal force against mortals should be unpalatable to most people and an act against their nature.
People who fling major power around indiscriminately should be regarded by people who know about them as maniacs and it will discourage people from working with and helping them. A lot of the supernatural world is political and social, reckless use of magic will seriously damage your credibility in any sort of tactful situation.