If his body is not fine, the club should give him break time to recover.
You have a good point there that Dortmund couldn't get close to Bayern Munich till the end of the season. Dortmund weren't even at the second place and there was a gap of 14 points between them and Bayern Munich. Haaland scored 27 goals in that season of Bundesliga. I must admit that Dortmund are playing much better as a team this season. In the end, they can't win titles being dependent on Haaland only.
When it comes to the injury topic, I hope that Haaland doesn't come back as a weaker player. He is going to be out for quite a long time in the end. But I believe in him to continue from where he left. He is a very special player and none of us would like to see him losing his perfect performance.
Reus just publicly announced that he is convinced Dortmund will become the next champion.... Hm, as much as I like Dortmund, but that is not going to happen. Will see when they face each other in a couple of weeks.
Regarding the injury, no, Haaland is a different type of player and he is also much more robust than the players you mentioned. He isn't really the kind of guy who get injured because of a tackle as he has a very strong physique. He is going to come back even stronger. I have no doubt about that.