Did a lot of figuring and can only conclude that you are correct. We know that Yoshida was not totally overmatched in the first half last year, including a bit of power. But he also went through many stretches of the topped, soft groundball to the right side , especially in the second half.
The problem, imo, is that he either doesn't know how or refuses to adapt to the pitching or his swing path. Duran is hitting over .300 because he is going to left field a lot, which includes ground ball through the over-shifted infielders. I'm sure the coaches are talking to him, but how much does he or his interpreter get and understand. The DH role may not suit him at all mentally, and given his culture. The placement there may have been a huge disrespect/insult/loss of face which Japanese give much weight to.