It seems to me that success in the Bundesliga is not really that important - the difference in income from first and second place is not much different. An important difference is the ability of the club to compete in European competition. For example Real Madrid lost La Liga this year, but in the Champions League they played just one game less than the maximum possible number and received a lot of money + advertising. Thus, their year turned out to be much more successful than that of Barcelona if we take purely finances. Dortmund need to aim not just for the Bundesliga title, but to represent something in the European arena.
Borussia Dortmund management never been gone for the title in Bundesliga or European competitions because their main business is buying youngsters and after few seasons Polish sell them at high price which is much better and profitable for them and they are having few good luxuries just because of their business role model and just because of this mind set Bayern Munich is enjoying good success in both level competitions because they are also having enough funds and their role model is also one of the best which is helping them for having enough quality players for the better results and win of trophies many times we discuss this here but Dortmund never been going to change their strategy and doing things as they want to do for having enough profit.