Barcelona really performed very incredible, I didn't expect Barcelona will defeat Dortmund so easily since I usually think Dortmund are performing good in the ucl more then the league competition, with this goal difference i don't think Dortmund can do anything in there home and defeat Barcelona in the uc for the second leg, in my opinion I think Dortmund will definitely be eliminated because they can't recover in the next match. Barcelona have mr chance then them in the competition and they have more key players then them this season, they should just performed and finished in top 4 in the Bundesliga so that they can get the opportunity to qualify to the next Champions league next season. I think is only inter Milan can give Barcelona tough time after the quarter finals, because am thinking they are in better shap and they can probably stop Bayern Munich in the second leg since they are even leading them with goal difference currently, and they will play at home, let see how the second leg will ended.
Barcelona is a good team, they've shown a high level of superiority against Dortmund, the victory and the goals was as if Barcelona was encountering a lower team, though in terms of football, Barcelona got a good history against Dortmund, so there's no way I was expecting anything aside Barcelona winning them but what surprised me was the number of goals involved, 4:0 is too much for a team like Dortmund, it is now obvious that they go nothing to do in the second leg just as you've said already.
I think Dortmund should go and prepare for next season that's if they'll qualify, with the look of things, there's no way Barcelona will be allowing them to equalize such number of goals and also win as the case may be unless they'll be doing some magic, personally I think Barcelona may even go to the finals, if they continue this way, football is about consistency and I believe Barcelona manager knows that already.