Sexuality in Eorzea seems to be very open and a case of 'anything goes' - homosexual and bisexual characters are regarded pretty much the same way as heterosexual characters. The exception seems to be the two male adventurers connected to the Wanderer's Palace HM quest, who state that the miqo'te of the pair was thrown out of his tribe for being gay, although that might be simply because he wasn't interested in satisfying the females of the tribe as a nuhn (the Sunseekers having a very rigid breeding tradition) and not because he was specifically gay.
Speaking of the Sunseekers, during a level 30ish quest for the U Tribe at Forgotten Springs (where the player helps shoo away peeping toms leching at female miqo'te bathers in the oasis, if your character is female the miqo'te quest npc will actually flirt with the player, suggesting that she is a lesbian.
And of course, this isn't the first time in the game where a female player character has been propositioned by another female npc - players who started in Ul'dah in 1.0 experienced this within the first minute of starting the game! (although as she was clearly a prostitute I guess that doesn't really count, but the fact she's clearly disappointed that you are unable to afford her 'services' perhaps hints she might prefer women anyway):
And still on 1.0, if you selected a miqo'te Path Companion in 1.0 if you also played a female character she then basically spends 90% of the time making passes at or flirting openly with your character (although she also stated she was enjoying sleeping with men too, such as the 'male friend' whom she got the location of Moonspore Grove from, it's a long story - making her technically bisexual in any event):
And that says nothing about the Ceremony of Eternal Bonding where same sex ceremonies are regarded exactly the same as a male-female ceremony. Then there was the vendor for the 'Rising' event in 2014 (the girl who was dressed as Minfilia from 1.0), who stated if selected 'small talk' reveals her wife made her the outfit.
Really, Eorzea is a very open place when it comes to sexuality, perhaps more so than real life.