If you have the resources to do a Hugelkultur bed, by all means, go for it.
It's not just about moisture, it's also about symbiotic bacteria and fungi. With the raised mound, you can also plant more per square foot, due to the increased surface area.
Here in my house by the ocean, my entire yard is sand, and the only thing that grows in it, is what one would consider weeds. However, in one spot, where there used to be a hardwood tree that was cut down to make room for the pool, we have a hibiscus that is always the deepest, darkest shade of green, and never gets fertilized. It's also the only spot in the yard where I can always find earthworms.
Go figure.