I love this subreddit so much for the quality and extent of responses. I'll try to address all your points. I really appreciate the effort you put into your response!

1) Those aren't the actual names of the races, that's just the English translation colloquial terminology that's used by most of the characters in my story. I could have told you the names in elven, I just didn't want to clutter my post with unnecessary information. I'm with you, though, that stuff bugs me too.

2) They have different religions, habits, etc., and are essentially the same physically.

This seems to be stated in contrast to the elves, putting you back where most fantasy settings are- very distinct human groups, and elves all just kind of... elfy.

The dark elves certainly are, but they're maybe at a 1:50 ratio with the wood elves. The wood elves are the diverse ones; there're those who cling to their old religion (entirely different from the one the dark elves follow, by the way), those who've accepted the way of the dominant human religion, those who are atheists, and those who follow the minor cults of one of the dark elven gods. Some travel in clans, yes, but there're city slaves and pirates and mercenary companies as well, all groups which have pretty high wood elf:not wood elf ratios.

Why exactly would your dark elves care about freeing the wood elves, if they're such distinct groups, especially given the dark elves' very different worldview and that the wood elves habitually raid their villages?

They care for the wood elves of the old religion, who periodically come to visit the elven capital and despite their differences with the dark elves will share food, give gifts, and catch up. Most of the other wood elves don't like them much, and a big plot point in my story is going to be how they address that majority when pondering their desire for wood elf liberation.

In fact, a lot of the atrocious stuff the dark elves do with their magic -- typically requiring blood sacrifice -- is at the expense of wood elves. Poachers and thieves who infringe upon the big elf city are punished with death. They certainly aren't bleeding-hearted "kin of my kin" types; even the wood elves who are respectful and invited as guests are viewed as childish and ignorant for clinging to old traditions instead of embracing the tangible benefits of worshipping their newer gods.

3) I agree 100%. Only the dark elves are isolationist, and even that's changing with the political tensions around the start of my story. They're also not particularly beautiful, I thought I should mention. They think themselves beautiful, yes, but they're quite odd-looking in their coloration and state after the havoc wreaked by their magic/summoning/lack of sleep. "Unnatural" is the word I use to describe them in my story.

A bit in the same vein, another caricature is the elf mage (and to a lesser extent the elf rogue). Let some of your elves be weird. Some humans want to be mages- maybe some elves think magic is an outdated relic, for example. Maybe have some elves who prefer large human cities.

Already on it! I'd almost say that a majority of wood elves consider the use of dark elven magic to be pompous and stupid. Even natural magic, to them, is seen as a tie to the dark elves who have somewhat indirectly led them to their oppression. I'm not sure about the enjoyment of human cities. There're self-hating wood elves, certainly, but even they wouldn't be accepted as equals. Perhaps on another continent, but in my story the elves who integrate with humans do so in countercultures (human mages, criminal organizations, mercenary companies, smugglers) rather than openly in society.

Just want to reiterate that I really appreciate your feedback. I'll definitely keep all of this in mind!