johntfs
Songster
It all depends! - If you are in an area with predatory birds, for example you should have drakes. They are the guardians of the flock, always watching out for any dangers to "their" girls and alerting them.
And yes, that mating thing. My ducks actually request to be mated a lot. They flatten out in front of the drakes, bob their heads and make demanding sounds to seduce the drakes. So i assume it is different for a duck to be mated by a drake vs. by another duck, because i also have duck-sandwiches from time to time… And triple duck-burgers…
From my point of view you do need drakes.
Figure like everything it's going to depend on your set up and situation. With a small flock an enclosed, secure run with good poultry netting might be a better defense than a drake. You seem to have a large flock and a pretty big "roaming" area for your ducks, so netting it off would be prohibitively expensive - in which case drakes could be very useful.
Just coming at it as an self-educated outsider who doesn't keep ducks, one thing I notice is that a goodly portion of the "cries for help" on the forum come down to "My drake is doing horrible stuff! How do we make it stop?"
So my take on the OP's question was that unless she just wanted to get fertilized eggs or breed ducklings, there's not much of a reason to get a drake and quite a few reasons not to get one.

My ducks are constantly doing the head Bob and accept any advances from the 2 drakes that have matured. I have pondered so much on keeping a Drake and adding ducks come Spring, but every single time I see the drakes mount the ducks in the pond, I am so terrified that they'll drown my ducks. I believe my Pekin duck experienced a near drowning not too long ago and that's what made up my mind. She was ok within a few hours, but like @Jpat has unfortunately experienced, drowning from mating, can and does happen. Now, if your ducks are in a run with a pool, or something shallow, that is different, I believe. As far as the drakes other functions, I haven't noticed my drakes doing a lot more than mating. My Pekin duck, Honey, seems to call the shots and I've noticed a few times where my Buff Duck takes charge. All of my ducks are young (hatched beginning of August 2019) so that could be part of my experience. Best of luck. Ducks are wonderful (Which you already know) and I wish you all the very best!