Well, watch it again, then. First of all, it couldn't be Reachmen because they are not part of Daggerfall Covenant, as stated by devs. In the last scene, it is visible that the Altmer woman IS taller than the Bosmers behind her, although not by much. We don't even know their gender. They could be females. Or she might be shorter than avarage Altmer for all we know.
Secondly, the hooded guy wears yellow-Blue, not yellow-black. And he definitely doesn't have yellowish skin. You might want to check settings of your screen. I think that's where your problem lies.
I watched it several times now and paused at the important parts. First of all, I did not say those are reachmen, I just said they are tribal, and Bretons are known to have tribal factions, like the reachmen. Secondly the two guys behind the elven mage are male and female, it's pretty obvious, unless the one on the left (from the viewer side) is a chick with a manly physique, which I doubt. The one on the right seems to be female and is smaller than the mage, but the one left, is not only taller than the one on the right, but atleast as tall as the mage.
Then I looked closer, and it seemed they have pointy elf like ears, but that might as well be part of that skull helmet. It's just too blurry to make out. But judging by height alone, I'm pretty sure the one on the left is no Bosmer. However we also don't get a good look at their faces, so he might be Khajiit. Atleast it said that there types of Khajiit that look almost like elves. On the other hand, I don't think we can customize our Khajiit to look like that so I doubt they would show them in a trailer (especially since it's a rather obscure lore reference, that most people wouldn't get).
Lastly, the hooded guy has blue straps on his armor, but whole thing looks black. And his skin looks more yellow-ish than the elf mage's face. Besides that, his facial structure looks more elfish than human. Too bad we can't see his ears, but I'm 90% sure that is an Altmer, while the elf mage looks like Bosmer (rather small, pink skin, nothing on her looks Altmer like.