80-100. 5 days. (8hrs game play everyday).
My ninja was the first legendary I got. He is difficult to level because he does die pretty much every raid that I do. He takes out a few key heroes usually before he goes, but then he is out of work for 15 mins unless you want to revive with gems.
I get about 30k to 40k exp using 3 heroes only depends if my heroes die alot or not but yah Ive been lvling my druid for at least 20 days and thats 100 to 114 so after 100 be patient cause its going to take awhile