A log curve, rather than linear, would make the bars in the center taller and not give the same appearance of a massive change in the measurement. Not for me to say, but I'm guessing that, as is, it doesn't represent the work put into the effort as well as possible.
Yes, that's what a log scale does to a graph. But why do you feel a log scale is appropriate in this situation? To me, a linear scale is a much better choice. The underlying data isn't necessarily exponential, so there isn't a compelling reason to use a log scale.