Yes, hard mode is definitely worth it. In fact, there is little reason to farm Normal Mode if you have access to Hard Mode.
Personally I farm for merch food in prophecies, there are very few non-inscriptable (nightfall only) rare skins that people want. Personally I find Vanquishing the Cursed Lands, Hydras, and Frost Minotaurs to be the most profitable of the Prophecies areas (outside of UW/FoW - which I detest doing). The Cursed Lands seems to have a *great* drop rate of golds if you are into title hunting.
For rare items, I don't really know. Rare has really changed with the introduction of Hard Mode. Other than the fact that Loot Scaling depressed the prices of pretty much anything it hasn't caused any change to rare items availability - they are exempt from the scaling anyway. They still drop as often or as little as they ever have - in fact with the anti-farming code gone you can farm a single spot as often as you wish. However, with the introduction of Hard Mode *all* places drop max damage/mod golds and the drop rate is greatly increased - remember things like max damage Sephis Axes or Dead Bows being worth a lot? Not anymore, I've had as many as 6 max damage Dead Bows drop in one thirty minute run.
As is, nearly all the old prophecies rares drop other places as non rares, are no longer rare because of HM, or you can get incribable ones. If you want to try and farm rare items then Nightfall is where you need to go - you have elemental swords, DoA items, and a few other "semi-rare" (icy/fiery bladed axes and such). Factions also has a very few left, but they are slowly loosing their value as people find places to farm them also (Hard Mode, of course). The few left (things like Mursaat Weapons) I don't see being sold much, I do not know if it is because no one is selling them or because no one wants them - I rather suspect that most people want insribable weapons and that skin is "old".
