I guess there's a bigger problem than portrayal of autism by only a few characters.
As has been said many times on this forum; "if you know one person with autism, you know one person with autism" (or something along those lines). And that makes it increasingly difficult to give a good portrayal of people on the spectrum. And if we want a good portrayal on tv it only gets harder, because from what I understand from media (be it books, games, series, movies) is that the general audience can't deal with a spectrum in general. If you're not a really stereotypical case to the extreme people will fail to see it. It's why it's a spectrum and also why people often say stuff like "but, you can do X, so you can't be autistic". The other side of the coin will be that minor difficulties, which might not neccesarily be attributed to being on the spectrum, might result in more people claiming their on the spectrum (and of course, a diagnosis is worth something when diagnosed by a professional, but suspected, self-diagnosed cases might increase waiting time for those who really need it).
What's perhaps important is to, and this goes for male and female role models for those on the spectrum, is to at least have a clear idea what these role models should be like. Thus far, I can't really think of any role model on the spectrum for myself as a guy. I'm not like rainman, and if someone thinks Sheldon is the role model or prime example; I'm not like him (and I doubt many, if any on this forum are).
I wonder if there's such a thing as having a blueprint that gives an accurate representation for the masses that's clear, not confusing and doesn't have the risk of the pitfall of being either "too much" of all possible symptoms or being dismissed as "it can't be that bad".