As a female, I never felt out of place romancing him. I don’t like assuming anyone’s sexuality based on their past or whatever gender they liked to seek out the most lol. If they're into you, they're into you. In Astarion's case, it was mostly his survival instinct.
I skimmed this thread and I can already see people going around in circles. You want to know why? Because the discussion of sexuality in this game is only going to lead to nowhere, especially when it's been made clear that everyone is playersexual. Astarion has nods to both genders, and I don't need to pull up a dialogue snippet - you can play the game yourself and clearly see it.
If we're talking about the past, wasn’t there also a line about Minthara having a high priestess as her first lover? Orin is also hinted to be a former lover of hers, in a very abusive kind of way. Should they also change “high priestess” to “high priest”, so men can feel better about romancing her? Don’t answer that lol. It’s just something to consider since you're so insistent about the gender ratio. “Handsome” is gender neutral btw, and that is a fact.
All in all, if you made this thread in hopes for them to change the gender of one of his past “lovers” (if you can even call it that) so you can feel better about romancing him as a female - I can only say good luck. I bet part of the reason why Larian made everyone playersexual to begin with is to prevent these arguments from even happening.