My feral adopted cat doesn't mess with my hens, but she on the small side and the girls usaully stay together as a pack..I don't doubt a large tom cat can take out a large hen.I also have seen large cats kill wild rabbits.
I wouldn't be so sure that you don't have racoons around.Racoons thrieve in urban areas.As long as their are people and garbage cans, they are around.You may not see them, dead or alive near you,most likely they are there.
Yes, dogs are a good deterate, but a hungry coon can be a crafty critter.It's good that you lock your birds up tight and have a fortified coop..!