I think it would depend on what character you play and how you present it.
One thing i have found distasteful in how most present it is either from a misunderstanding of what it is to be a homosexual (Ignorance of sexuality in general) or falling back to stereotypes of what a homosexual is. Another issue is how you perceive the culture your character is from or in and how that society would handle said orientation.
First the problems I have with how it's Roleplayed by some. Two problems arise.
- Gay for a reason: Basically someone has a traumatic past or life altering event that "turns them". So for a female character it was "I was %@#!d" or "Men are abusive" or what have you. Someone who is Homosexual or Bisexual general just is that way, similar to how someone is Heterosexual.
- Sexuality becomes the center: Basically the flameboint character or the character for whom their homosexuality or bisexuality is so center to the character and what they do when they RP that honestly they are nothing but either stereotypes (Lisps, butchness ect) or that the only thing you can definitively know about the character is their sexuality.
The above two things are often what I see when someone tries to portray a homosexual character or when sexuality becomes an element of their character. (Especially when it's an important one).
The next issue is culture. Granted, Blizz does not lend clues as to how the fictional societies and cultures on Azeroth handle issues of gender and sexuality. To a certain extent it will be a personal aesthetic judgement.
With my own character, she has stated and been fairly frank when asked, that she is in fact a bisexual. She has no reason for being so, simply she just is and that is the end of it. She just has always seen beauty in either gender. I don't go around IC seducing folks or flirting but when asked "So, who have your past lovers been?" she will honestly state them. This I attribute to her being of Highborne origins and what I interpret to be a caste that was somewhat more sexually liberal and open to that sort of thing. It's not an important aspect of my Roleplay though if it comes up, it's there. And there is no reason for this orientation, merely she was born and that was that.