Waterfowl and ground birds are not meant to be housed together. They have nothing in common except that they are birds and they eat the same general type of feed. All similarities end there, though.
Ducks are not evil, but they have the ability to out-compete any other poultry for resources. They are survivors. They out-lay, out-eat, out-forage, out-breed, out-hide and out-drink any other birds. Once you know that about them you must make sure that no other bird is in competition with them because the other birds don't stand a chance against ducks. It is for these reasons I have always housed my waterfowl separately from my chickens. (Not to mention, my chickens would divorce me if I tried to house them with the sloppy, water-loving, messy ducks.)
Then there is the breeding thing. A roo can "mate" a duck and have no issues from it. A drake tries to "mate" a chicken and you have a wounded hen. A dangerous situation for your hens to be in.
I have kept chickens, ducks, and geese for several years now. They are housed separately, stick to their own groups and rarely interact with each other. I have chosen not to keep drakes or ganders because they were too difficult. This has worked out very well. The population is stable, the fighting is minimal, the girls are not harassed constantly, and everything is peaceful.
Good luck.