I think Arsenal will win the group because seeing Arsenal's game in the EPL this season is quite good with 3 wins and 1 draw. For second place, maybe Sevilla, why Sevilla? Even though it is not doing well in the league, in the European arena it cannot be underestimated. PSV is indeed good but in my opinion it will occupy the 3rd and final position, definitely Lens
Looking at the composition of group B, I have to agree with you regarding Arsenal chances of winning the group. However, I am a little doubtful of Sevilla runner up position and prefer to place PSV in that position. I don't doubt Sevilla quality and mentality when playing in the Europa League competition, thanks to winning it last season Sevilla qualified for the UCL automatically. I think everyone knows how Sevilla has performed in La Liga this season, they are not as strong as last season. With these facts, it can be predicted that Sevilla will find it difficult to qualify from the group phase.
However, that doesn't mean it's impossible for Sevilla to qualify from the group phase, anything is possible. It could even be that Arsenal, the favorite to win the group, experiences a decline in performance and the situation turns upside down.