Sciffy generally doesn't do too well in that regard. Eureka is the exception, as far as I know, although there are a couple of shows that I don't watch.
It's a mixed bag. Warehouse 13
does have an overly white cast, and has just killed off its only black regular, but it has a fairly diverse supporting cast including CCH Pounder and Faran Tahir in major roles. It's also relatively progressive with gay/lesbian characters; regular character Steve Jinks is gay (though in a kind of asexual way, since he's not with anyone) and there's a strongly implied lesbian attraction between Myka and recurring character Helena Wells.
As far as I know, Haven
's cast is pretty much white, but I don't watch it. And the upcoming Defiance
's regular cast includes one First Nations (native Canadian) actor, Graham Greene, but otherwise is overwhelmingly white.
As for the Canadian imports, Lost Girl
is quite good with the LGBT representation (its lead character is totally bisexual and currently in a committed lesbian relationship), but not as strong in the diversity category. It does have one black semiregular, K.C. Collins (and a second, Cle Bennett, in the first season only), and one semiregular Little Person, Rick Howland. So some kinds of diversity are represented better there than others. Continuum
, meanwhile, has a nicely diverse supporting/semiregular cast including Roger Cross, Lexa Doig, Omari Newton, Terry Chen, Stephen Lobo (who's of Indian and Iranian ancestry), and Jennifer Spence (who's part-Japanese) -- but unfortunately, except for Spence, all of them play bad guys (though Lobo's character is morally ambiguous).
So I guess you're right about Eureka
being an exception. Which is too bad. A science fiction-oriented network should be leading in inclusive casting, not trailing. But as we've seen many times, as a commercial network it's obliged to make choices based more on ratings and profits than science-fictional principles.