Lemme set this straight... evil biomes SUCK... but I like the way they suck. I wouldn't mind if they sucked more. But every other aspect of the game that involves a considerable amount of risk also comes with significant rewards. Breaching the cavern levels gets you access to underground trees, better the further you go. Magma... is just amazing, yet has its own risks associated with it, not the least of which being in the form of fiery, fiery death either from the magma itself or... other things associated with it. Cotton candy's the best stuff there is... but has its own very significant risks. As it stands, in terms of alignment, good biomes give good reward (the best booze in the game, and very useful wood) for no risk, whereas with evil the rewards are a lot less in terms of practical uses. Sure there's silver dye and really heavy wood, but really heavy wood is only really useful for things made of wood that get a bonus from being heavy... like wooden arrows and weapons. Talk about elves? And silver dye's barely even cosmetic, except for the higher value which is kinda moot because you're probably not going to be doing a whole lot of caravan trading regardless....
All I'm saying is add in a little reward for having the stones to face off against the constant stream of undead, toxic clouds, rain that can melt your skin, and masses of reanimating, dividing enemies that can melt your CPU. Maybe not even something that's just a better version of stuff elsewhere, but an interesting new mechanic to play with? Undead slave labor? Tameable undead beasts? Willing zombification for certain benefits at the expense of others, like vampirism/werewolves? Lots of possibilities.