All the gay characters have been filled with angst, Dorian and Cortez while all the lesbian options have been very happy and fluffy like with Sera and Samantha. I smell a conspiracy, I think Bioware is trying to change the definition of gay to mean sad instead.
Well, at least no gay character have to end up: being cheated on, die no matter what, and having to make the LI impregnate another woman just to stay both alive. I think is mostly a cospiracy against male LIs in general, with particular rage towards straight female characters.
On Topic, I wasn't much into Kaidan. I romance him in ME1 because he was the only option for my straight female character, and than I leave him in ME2. I always found him boring at best. (not as much as Jacob, but still...) And I think his character really is flat if he is not in a romance (romance that I find quite cliche and very little interesting.). In my last run in ME3 I almost forgot that I had him in the team.