FWIW, you might want to take a look at
ridewithGPS. Mapmyride is notorious for - I don't know the correct way to say this, but their contour lines are very far apart, so they
drastically underestimate grade and total elevation gain if you live in an area with short, steep hills. I don't have much doubt that your hill is a LOT tougher than Mapmyride says it is.