Regarding Macdonald, the following is appropriate: 'For generations his true character has been obscured by the sympathy English writers felt for him because of his ancestry.'-John Elting. It looks like you've fallen into that trap.
Regarding the Katzbach, Macdonald crossed the river against the express orders of Napoleon. You don't put a river at your back when you're going to fight.
If you'd like to see an excellent map of Leipzig and the terrain around the city, see the Esposito/Elting Atlas, Maps 141-143. The swampy terrain between the Elster and the Pleisse are clearly shown.
I'm very aware that I wasn't at Leipzig, but I know how to build and emplace a bridge and how not to defend in front of a river line.