I don't know if it's the area of the country or what, but I have actually found duck eggs easier to incubate than chicken eggs? I have found, as with most incubating, that the temps need to be as steady and possible and the incubator opened no more often than needed. However, that is common sense,lol.
They do need more humidity than chicken eggs, I leave it at 55 percent during the first 25 days then up it to about 60 percent. Also, when turning the eggs (if you don't have an egg turner), it helps to turn them end over end instead of side to side.
After the 7th day, on one of the times I turn them, I mist them with lukewarm water and let them cool from 10 to 15 minutes.
I don't know if any of this applies to bantam ducks though! I admit ignorance on that subject which I am hoping to remedy soon.
I've gotten great development but am still losing more ducklings during the hatch than I do chicks...so just trying to figure out if there's something that I'm missing. I had heard about the misting/cooling periods - I may try that one on this latest batch to see if I can up their chances of a successful hatch.
Look in the stickies at the top of the duck forum main page. There are at least two threads on hatching ducklings.
Also, there is often confusion between wet bulb humidity and relative humidity. They are not the same thing. Too humid conditions have caused a number of losses in duck egg hatching from what I have seen on this forum.
Opening the incubator too late in the process is another thing I see happening.