It has to match what the job duties letter says. If your company gives you a letter that says you were in different roles with different duties, it's better to break it out otherwise it will look odd.
Personally, I would break it out by position.
Jan 2013-Jan 2014: Junior XYZ
Jan 2014 - Jan 2016 - Senior XYZ
Jan 2016- Current - Director of XYZ
That shows a normal career progression and will be backed up by the letter you get from your HR.