Any time anything in your steering or suspension breaks you could have a very dangerous situation. Properly engineered quality parts installed correctly is the answer.
I've not run mono-leafs on an AD truck but if the parts are well designed and manufactured I'd not be afraid of them. I have a car with fiberglass mono-leafs and spring failure is not common on them.
Years ago I had a Blazer with mono-leafs and I beat it up enough to break the spring mounts (and other things), but never had any trouble with the springs themselves.
Anytime you change the relationship of the spindles to the steering you may need to make adjustments to prevent bump steer. Relative to the steering box dropping your truck with a mono-leaf isn't any different than dropping the axle.
You can combine lowering methods such as mono-leafs and a
dropped axle to achieve more drop. You need to watch the tie-rod and steering arm locations to be sure you're not causing trouble.
Look for trucks that have the stance you want at car shows and crawl under with your camera to see how they did it. Asking the owners is good too, but I've found that often the guy showing a truck doesn't actually know how it was built.
