Half the squad was injured during the first half of the season, when they started coming back they picked up massively over the second half of the season and still managed to qualify for Europe, they lost probably the best outright striker in the world as well as you said, hardly an inconsequential thing
and No Dave we would get beaten by Tuchels Dortmund, we are not a better team than comfortably the second best team in Germany, they have a better set of players and they have a better manager as well, and how exactly was the team found out, they had a ridiculous injury record the first half of the season, once the player came back they shot up the league massively, all the seasons before they were battling at the top, the season after they are right back up at the top.
Aye Dortmund got found out massively though as you say
2011 - 1st
2012 - 1st & cup winners
2013 - 2nd & Champions League runners up
2014 -2nd & cup runners up
2015 - 7th & cup runners up
2016 - currently 2nd in the league
yeah they got found out so massively mate