Dortmund's opponent in the last 16 of the Champions League is the leader of the Dutch Eredivisie, which Dortmund basically cannot underestimate. Because PSV is a team that has amazing strength in its local league, Dortmund needs to play well enough and not make too many mistakes. Because in this round of 16, all teams will try better in order to qualify for the more challenging round, namely the last eight, so Dortmund needs to perform as well as possible to win at PSV's home ground.
Actually PSV is not really difficult opponent team for Dortmund on 16 round of Champion League depend have to face top teams from La Liga, Premier League or Serie A. Current standings, PSV lead top position awhile and have most impressive performance in domestic league with 16 won of 16 matches and not get loss or draw yet. But Eredivisie not really compete such as Bundesliga have many top teams with Dortmund can improving their performance get chance qualify to quarter final.
PSV group phase in Champion League not really difficult than Dortmund success eliminated AC Milan and defeat PSG to lead top position standings, I think Dortmund have bigger chance qualify to next round than PSV.