Alex B. wrote:
... and all the awesome organic material was dry as tinder in the keyhole but still nice and moist in my traditional raised beds.
For better or worse, a raised mound has more surface area exposed, and it will 1) heat up and cool down faster when the temperature moves in one direction, and 2) dry out faster compared to a flattish raised bed. It might also absorb less water, as the slope will shed water in a summer downpour. In cool/moist conditions, the raised surfaces are an advantage; in a hot/dry conditions, the swales in between the ridges are more favorable.
Once a tree is established, it can do ok in either the hill or valley of a micro-topology. Even with good design, a period of drought or low rain can take a toll - just less of one initially, as good designs are buffered and more stable, but not insulated from the elements.