Yeah, every low quality player at Dortmund was signed by Klopp, every great one by the board!
Klopp has already signed four for Liverpool who will most likely be looked upon as exceptional players - Mane, Karius, Matip and Grujic.
Previous post from Dortmund fan Sphaero -
The final call was a group decision amongst the three of them. Every party had the chance to veto. As far as I know there are two cases which became public of that happening. The first one was the wish of Zorc and Watzke to replace Lewandowski with Mario Mandzukic, which was vetoed by Klopp as he was not a fan of the Croatians personality. The other one was Zorc vetoing Klopp´s plan to sell Aubameyang after his first less than ideal year with us.
Normally, the process of recruting at Dortmund worked along these lines:
1. Klopp expressed to Zorc wishes of certain player types and profiles which he liked to implement in the following season
2. Zorc gave out the profiles to the scouts and eventually compiled a list of potential candidates which was given to Watzke
3. Watzke checked the list from the financial aspect and narrowed it down to the realistic options.
4. Klopp and his co coaches viewed material themselves (sometimes visited live games).
5. The three came together the first time and see if there was consent between them. First chance to veto by either party.
6. Watzke/Zorc or other officials approached players and agents if there was interest in joining Dortmund and the clubs under what circumstances they were willing to sell.
7. Klopp talked with the players themselves, assessed their personality/motivation and sometimes tried to persuade them to join.
8. The chosen candidate was discussed a second time between the three of them with the second chance to veto.
9. Personal terms of the players were finalised by Zorc and neogtiations with the clubs were held by either Zorc or Watzke (mostly the former).
That is of course the regular case. There were also cases where players were directly suggested by Klopp. Neven Subotic and Ciro Immobile forexample were such cases.