One of the main reasons that Kerfoot was so effective in Colorado was that he received a fair amount of power play time - a luxury he simply doesn't have in Toronto. After scoring 22 power play points and 20 power play points in his rookie and sophomore seasons with the Avs, Kerfoot saw only occasional use on the man advantage in Toronto, being limited to just 1 goal and 3 assists in his first year with the Leafs. He saw his special teams usage shifted largely to a PK role.
During his first season in Toronto, Kerfoot shot just 10.2%. His next two seasons saw him shoot 11.8% and 11.1%, respectively - not far below his career average, but still vastly higher than the current 2.6% that he's shot this season. Even though he has been a primary penalty killer for the Buds and receives very little power play time, Kerfoot has still been scoring at a decent rate for the volume of shots he takes. This year, he has simply been a little more snake-bitten than normal. This corresponds with the eye test as well. We've seen a number of clear-cut breakaways for Kerfoot this season and, for one reason or another, he simply can't get the puck across the goal line.
The law of averages says this problem will sort itself out. While Kerfoot may not reach his career average shooting percentage of 12.8%, he should certainly finish a lot higher than his current 2.6%. Bad luck can only last for so long. If he's shooting at 12.8% over a 386-game span, that's a pretty substantial sample size and give us cause to believe that his current struggles will not continue for too long.