I want to like BBT, but I'm not a fan of the jokes largely built around casual sexism and misogny, and the nerdy stuff strikes me as a bit exploitative, like blaxploitation shows in the 70's. The few times I've watched, though, Raj definitely seemed closeted gay to me.
As for Loki, MCU (movie) Loki is probably asexual, at least the way Hiddleston portrays him. But in the comics, a couple of years ago he was regressed to a teen (I think now a young adult), and the writer has definitely been writing him with more than a little hint of queerness. I plan on picking up the comic to see how well it comes across. Comics don't have a lot of finesse when it comes to trans characters, but a few writers are trying (Gail Simone made Batgirl's roommate a trans woman, for example).
As for Dr. Who -- not going to happen as long as Moffatt is in charge, I'm afraid. :/