To the best of my knowledge that is correct, so what you then need is a map to determine what will drop from the specific node you are visiting.

However, each group of nodes share the same set of items, with each type of node dropping a subset of those items.

A certain type of item is also ALWAYS found at the same depth. For example, mythril can always be found at the third-highest notch wherever it is found and gold sand can always be found at the third lowest notch if it is available to be found at that node.

It's in the latter two parts here that this chart is helpful. It gives you a broad idea of what you can find at a given camp region and what depth to mine at, level to cut at, point to fish at, to try and get a specific item with the highest level of probability.