Having better squad did not help PSG to win Dortmund in group stage and it is not good for their mentally support before two semi final matches. I know big difference between group-stage matches and semi final matches but their previous two matches in this season, are good evidences that Dortmund are not a weak opponent for PSG. PSG in theory are stronger but they have to do a lot of things to beat Dortmund in semi finals.
We know Dortmund are more experienced in this competition and because of that they are not an opponent to be underestimated. Even PSG's size certainly won't be able to win easily and instead Dortmund will put pressure on them. I think the difference in squad depth will not apply in the Champions League and the most important thing is the mentality of each team itself.
Dortmund proved to be the champions of the hellish group at the start of the season and stopped other strong teams such as Newcastle and Milan. Now they will face the same opponents as in the previous group and I am sure they will have no problem getting a ticket to the Champions League final.