Were the "sexy" Jace and Sarkhan you were photagraphed with at the party fans or hired by WotC. If they were hired - you know that's the kind of things that turn potential female players away from the game, right?
The only cosplayers hired by Wizards were the five members of the clans. Everyone else at the party was cosplaying because they wanted to.
You slut shaming cosplayers is what turns us against people. WotC does an AMAZING job representing powerful, diverse, strong women (wearing practical things). Also, genderbending characters like they did, usually involves making the character more feminine/sexy but it’s totally up to the cosplayer to wear something they feel comfortable in, if it’s sexy, so be it.
You don’t know what you’re talking about.