I can certainly see why the OP (and other people) would be sensitive to the subject, but I personally don't see that much of a problem. As a gay Trek fan too, obviously I love to see all sexualities represented in Trek Lit. But I don't feel like "We" have been targeted unduly for pain and heartache.
Plenty of straight couples have broken up or had a partner die both on screen and in Lit. Even if we take screen canon out of the equation (since of course there are no gays on TV) I don't feel like LGBT-specific relationship trauma is of a higher proportion. If we take the 10% rule into account (mostly untrue but useful for some purposes), then of all the Lit-original characters, only a 10th would be LGBT, and I think the Lit has fulfilled if not exceeded that nicely.
If I were to accept the premise that it seems like LGBTs are unduly targeted, and if I were to come up with an explanation, then it would be a combination of some or all of the reasons that have already been stated in this thread. In universe, the military is a dangerous occupation and people are going to die. Out of universe, drama comes from conflict. Nothing more sinister than that. If anything, I think it shows more inclusiveness, not less. LGBT people in Trek Lit live exactly the same lives as the heteros.
I too am a member of AfterElton, and upon their recent announcement that Warehouse 13
would now feature a gay character, I commented that I was getting a bit tired of TV showrunners and cast members proudly stating that they have a gay character "but that their sexuality doesn't define them." I mean, it's saying the right thing, but that they are saying it at all kind of puts the lie to what they are saying. It seems to come from a place that thinks that gay people ARE just defined by their sexuality, but "aren't we being progressive by saying that's not the case here." They're making an issue of it not being an issue.
I bring that up because I think that Trek Lit specifically doesn't do that - is better
than that. In Trek Lit, LGBTs really aren't defined by their sexuality, and we don't need to be told so because it's the baseline that we start from in the first place. Keru doesn't walk onto the page with an internal monologue of "Yes, he's gay, but it doesn't define him." He's just gay. It really isn't an issue. And part of that is that gay people suffer the same relationship problems, including breakups and deaths, that everyone else does. As always, literature is light years of TV.