This is ridiculous.
Gaider said Dorian is the first homosexual character he has written ('fully gay' were the exact words). That is what Gaider said. He never said Dorian was Bioware's first gay male (which is Steve), or first gay character (which was Juhani, unless one does consider gay only to apply to men (I don't, but whatever), in which it was still Steve). News sites will run with that however they like: is anyone really surprised that news takes one sentence someone made completely out of context to shift it in to something completely different in order to have a more SENSATIONAL headline? Because if so, I have bad news for you; the news is doing it *all* the time. All the time. Right now. Seriously, they're doing it right this second. 
Why is Sera not getting as much attention? Because of Juhani. Knights of the Old Republic. Came out in 2003. Remember that game? Stared fan favorite Darth Revan, pushed an era in to huge popularity for Star Wars marketing, spawned a sequal by Obsidian and an MMO by Bioware? IT EXISTED. Juhani was in it! She was a Cathar Jedi! You could recruit her! She followed you around! And she was lesbian! Had a huge crush on the female protagonist no matter what you did, and often confessed her love even if you basically ignored her/were totally in to Carth! Some people could get a bug that allowed her confession to show up for guys (but none of her other romance dialog), but that was at least patched out (or they tried to patch it out, at any rate) of the PC version, I know. SHE EXISTED, TOO. Not to mention we've had Leianna, who unlike some of the guys mentioned below, seemed to prefer woman (in game, there's like five more times to trigger her romance as a gal then there is as a guy).
There's also the quiet thought that former love interests by bioware who could be romanced as a male by male mostly seemed to prefer woman- Sky, Zev and Kaiden in paticular (Zev, in fact, is basically like 'Hey, boyfriend, I like woman better!' which, uh- thanks, dear, while the other two it implies that they're normally straight, but the male protagonist is just that special someone they make exceptions for, which... sounds like a lot of slash fiction I've read rather then how things actually work, in truth). DAII did better in that regard, but there's still the issue with Anders never mentioning the fact that he just killed his former lover to a female Hawke (or ever mentioning he also liked dudes), and Fenris will never bring it up to a female Hawke either and hooks up with Isabella (having said that and to be fair, Merill doesn't bring up liking gals to a male Hawke, either, so that was just a sort of thing with the game in which everyone was by word of god bi but never mentioned it, ever). Then we go back to the issue of Steve, who while a very well written character, his romance just seemed horrible: you are romancing a guy who's husband basically just died a year ago who he's still listening to voice recordings of and crying over. Help him move on and learn to enjoy life, awesome! Romance him? I felt like a major creeper when I tried it. So Dorian, in some ways, felt like the first full romance for a male who liked males that didn't lean on either 'He only likes you because you because you're special and would proabbly prefer if you were a woman'/'HIS HUSBAND JUST DIED', which aren't very fun ways to lean.
As for the ridiculous thing that Sera is just fanservice for guys: first, tongue in cheek, if they were going to make a character just fanservice for male f/f fans to get their rocks off, don't you think they would have made her 'prettier' (I think she's cute, personally) and less abrasive? Sera is there for people who like Sera. Yes, she does show skin- but so do most of the romances (Solas and Josie obviously don't, and I don't think you see much of Blackwall (just your poor naked Inquisitor when he abandons her, jerk), but I think the others all show skin). I think Bioware has stayed away from 'f/f relationship just to add fanservice'- with one notable exception in Samantha.
(Who, sadly, was a well developed character for someone just hanging around the ship (I liked her and Steve!), I thought- but the random shower scene and the bath scene also showing up for male Shepards sort of was... awkward. Very awkward. Not the best design choice.)
Oh, and just to make a note- gals not liking m/m? Hah. Every gal in the world is different, but seriously, do you know how huge yaoi/shounen ai/BL is? And over here in the West and pertaining to the subject... go to Archive of Our Own. Search Anders.
You're going to find pairings of him with fem!Hawke and occasionally the female Warden (and even more occasionally, Isabella or Merill, but that's pretty rare), but him with male!Hawke and Fenris are going to dwarf them (Fenders is huge on the internet!). And those are the only four gals I ever really see him with (and finding Isabella or Merill works is hard!), while there's still strong shippers of him with the male!Warden, Nate and Justice (...those are mostly AU's, I think?). There are still smaller groups shipping him with Varric and now Dorian or even the male!Inquisitor, too- not to mention Zev, or Cullen, or Seb. And the majority of those? Written by woman, which you can find by following their links back to their own tumblrs and the like.
Some guys think f/f is gross, and some gals think m/m is gross. But I don't think there are less female m/m shippers then there are male f/f shippers: they're just on different parts of the 'internet'. It's big enough for all of us, after all.