So, basically you think they wont gate anyone from humans, for sure? Hmm. That's possible. They are the large majority of PCs.
Dorian gated against qunari is another possibility I remembered. Tevinter has strong conflict with them, and it's possible he has an aversion. Solas doesn't like Iron Bull, so it's possible he has some reservations towards them, as well. We're not really sure where he's from, so it's possible he also had bad experience with them at some point. He apparently knows enough about them to have a strong opinion, so maybe he used to live around them?
I think no human LI will be gated against humans. That leaves Sera, the Bull, Solas, and Varric. The Bull is right out, and Solas has that whole 'open-minded' thing going for him (which is why, if he's gated, it'll have to be from something major, like a lack of Fade connection). While Sera has a thing against nobles, another poster brought up a good point: technically, only human rogues and warriors are noble. So, unless Sera is gender and race and class gated, I think she'll be open to humans. Now, Varric has specifically stated he's not into humans (yes, yes, he could have been joking, I know) thus he would be the only one who I'd believe would be gated against humans.
I think it's between Solas or Varric for one of the LI slots. Unless Vivienne isn't an LI, in which case both of them are. I think I read (or heard--perhaps one of the GaymerX panels) somewhere that, at one point, not all the race/sexuality setups were getting more than one option. Since the Iron Bull was the one they ended up working on, I think it was gay dwarves. Thus, I'm thinking that a dwarf-gated Solas or a straight-Varric are part of the remaining LI pair. Either that, or Dorian is gated against dwarves which... would be odd because dwarves are really respected in Tevinter.
Granted, this is all a theory since I can't remember where I heard about the initial imbalance. 