The 3.4% will change as more cases are included. As others have noted, the mortality rate is skewed by the high figure in Wuhan.
It is inconceivable, given the range of symptoms, that there aren't any cases where the illness was so mild that the person didn't report it (take the early UK case arising from the visit to Singapore).
Your suggested range of 20-60 x worse than 'seasonal flu' almost certainly doesn't take into account the effect of the vaccine. In terms of virulence you would need to allow for that; without the protection for vulnerable groups and elderly flu would be much worse.
Originally Posted by: Gandalf The White