Sorry I forgot to write before... the parameters are OFFSETA 1,65; OFFSETB 1,65; RADIUS2 15km.
Anyway, in arcmap 10.1 there is just the viewshed tool (not viewshed 2).
Therefore, I applied the combine tool to the viewshed results, since I used a tool planned for acquired the fuzzy viewshed I thought that perhaps my parameters were considered more in the viewshed result then in the fuzzy one. I presume that it works, as in the viewshed 2 sample that you posted.