Hmmm. I think the Dom/sub issue has been covered. But I want to comment on the straight/bi/gay thing.
Almost no one is TOTALLY straight, TOTALLY gay or TOTALLY bi. There's a famous study by Kinsey, who developed a scale from 0-6, 0 being 100% straight, 6 100% gay and 3 exactly 50% of each. He had all kinds of people take his test. And it is not at all clear and defined. And it is not constant. You could be a 1 today, and have a life changing experience in a year and be a 5 before sliding back down to a 2.
I don't know of any studies on the subject, but I'm fairly certain that a similar scale would work for submissive/switch/dominant.
Finding a PERFECTLY straight, dominant man is going to leave you searching for a long time, because both traits, in the pure sense, are rare. What should matter is, he wants to fulfill the role you want from him. (for you, he is dominant and straight, and is happy that way.) If you find out otherwise in the course of conversation, then you haven't been deceived than you would be by finding out his dearest fetish is your hardest limit, and vice versa.
And I don't want to point fingers but I have to comment on the use of the phrase "waste of time." It should never be a waste of time to talk to someone and get to know them, especially if it is only because they aren't as straight/gay/sub/whatever as you thought they were. Even if they aren't your dream play partner, you still met someone new and probably learned something or enjoyed your time.
If we really need to find a play partner/mate/friend that precisely fits our criteria, without in depth conversation, hand out a survey and problem solved. (although, it would make a hilarious scene, i'm imagining a play party somewhere, toys are out, every one is in kink-wear and as people are beginning to move towards the toys, this burly, manly Dom walks up to this mouse of a girl and hands her a three page survey. Do I meet your standards? ... lol)
But maybe I'm just misinterpreting the use of the phrase "waste of time." If so, just ignore that little mini rant. (although i really would like to see some of the Doms here reduced to the point of "applying" for a position -giggle-)
SP