I actually think this is a duck experience vs a breed one. I have had A LOT of Muscovy drakes(into the teens) and only had one that went wonky, i still keep two. Sadly, some drakes are aggressive, it just happens and because you got these birds as adults it's hard to say how the bird was raised.
It really is to bad you had a negative experience as Muscovy are a decent duck.
Well, it was a bit of both, actually.
The drake never mated the girls that I saw. I mean, I'm not up there 24-7 or anything, but I'm up there A LOT and I never saw him even attempt to mate them, except once, and he failed.
1 hen hatched out a clutch, but she had a
ton of difficulties. She chose a bad nesting spot, so the hens harassed her, causing eggs to roll out from under her all the time. When it was finally hatch time fire ants got into her nest so I took the eggs and finished them in the incubator where they would be safe. (I tried to move her, but that was a total flop. Also my flock had pox at the time and I was afraid the babies would get it.) So I gave her a lonely Wyandotte chick (who's brother had recently died, so he was all alone) so she was satisfied that she had a baby, and I moved her to a tractor. When the ducklings hatched I slipped them underneath her. She refused to sit on them and keep them warm because she was devoted to Thor (the chick) who was more active, so she followed him around instead of watching her duck babies. I put her in a tote and made her sit on them over night. By the next morning she was watching her babies carefully and became a devoted mother to both ducklings and Thor.
As the ducklings got older, only some got bigger. 4 ended up not growing correctly and dying with weird symptoms. One had vet confirmed Aspergillos (or however you say/spell that), but she also had a heart defect. They all died the same weird death. First losing strength, then coordination, flopping over backwards (It wasn't that duck disease that makes them fall over backwards. I forget what it it's called. But this was different. I don't know how to explain it.) and not able to get up up, eventually spasming, curling their neck back, and dying.
The remaining 3 grew into healthy, beautiful girls.
But overall the problems I had were, they weren't producing anything for us. They were supposed to be meat birds, but they weren't really producing and what they were producing was dying! They did a good job of keeping the flies down for a while, but even that slacked off. They ate way too much to not be producing anything for us. I was willing to wait until the weather warmed up to see if they would do better producing next year until the drake started attacking everything.
After ALL that I guess I was just fed up. They are happier where they are at, and I'm happier without the stress of worrying if the drake will hurt my chickens, or if they are actually going to produce for us, etc.
A couple laying girls will be a good fit for us, though, I think.
(Sorry this is so long, believe it or not I skipped over a ton.)