The phrase "a bit of overkill" is correct and usable in written English.
It can be used to describe a situation where something is excessive or more than what is necessary for a particular purpose.
Example: "Using a sledgehammer to crack a nut is a bit of overkill."
Alternatives: "a bit excessive" or "a bit too much".
"The intercooler might have been a bit of overkill," he said.
But I think we might be dealing with a bit of overkill here.
Now, OK, most will feel with regard to child pornography a bit of overkill may be justified, but with "extremism" we start a whole new ball game.
I can also set an alarm not only for, say, 8 30 a.m., but for a specific time on any day within a calendar year, although I have always thought this feature to be a bit of overkill.
Our Colorado imports -- rugged, fat-wheeled mountain bikes -- were a bit of overkill for genteel cycling through rice paddies and along a landscaped coastal road called the Flower Line.
Mr. Marsh's lawyer, McCracken Poston, said then that it was "a bit of overkill" in a case "where none of the allegations had anything to do with a living being". Mr. Poston has continually made similar observations in the face of an impassioned community.
Still, when photographing small individual objects like coins or jewelry, a lighting tent can seem like a bit of expensive overkill.
If anything, Isaacson engages in a bit of scholarly overkill at the end, providing a separate conclusion and epilogue on Franklin's legacy, a chronology of important dates, brief biographies of all the supporting characters in the story, conversion tables that provide modern dollar equivalents for British and colonial currency, an annotated bibliography and about 50 pages of endnotes.
In short it's a bit of glorious overkill.
Otherwise, this kind of absolute precision seems like a bit of office overkill.
