I remember the most commonly used potions in FFXI were Silent Oil and Prism Powder. I would have a stack of these on me at all times, up until I hit lvl 30 or so. But, I agree potions in general should be more useful and phoenix down would be a goal/grail for crafters.

The problem I see however, is that if this was introduced as a recipe, many people would probably jump to ALC to craft it. To prevent the Phoenix Down from being abused for either profit or leveling, I think the NM idea is nice, but maybe it would also require higher crafting skills on other DoH classes as well. For instance ALC for its spell-like quality, WEA for the down itself, and BLS for materia (if it is later included), could be required to complete the recipe. I also believe if it were to come from a NM, it should be Rare/Ex, or if crafted, Rare only. Additionally, (though I was never crazy about it in XI), this may be a good use of the charge system, where one Phoenix Down has x number of charges with a reset timer of a week.

Just a thought.