I am not sure if Dortmund will qualify for the knockout round. Despite being at the top of the group, this team's performance has been erratic. In the last two matches they will play against Milan and PSG. And in both these matches they have a big chance to lose. I will hold myself back from betting on Dortmund in these two matches. My two favorite teams from Group F are Milan and PSG. Both teams will probably play in the Round of 16.
The performance of the Barcelona team is quite erratic. If you want to dominate the Champions League, it is important to have consistency in performance. Barcelona has no consistency in performance. Xavi needs to work harder to strengthen his attack. But Madrid, City and Munich are very strong this season.
Milan? They have to be the most Inconsistent side in this group f. They lose another game and their manager could be the next in line to lose his job this season.
Paris Saint Germans also, they just a coach that's experienced in the Champions League and they can boast of qualifications.
Barcelona will pick up, I will doubt that they'll be winners of the Champions League, like you said, Real Madrid, Bayern Munich, and Manchester City also Inter Milan are possible potential winners and favorites to win the Champions League.
Barcelona though, have that depth to win the La Liga this season. It won't be difficult if they are determined and consistent.