Sorry, but that's just dead wrong. Yen specifically is described as an ex-hunchback healed (but not fully healed) by magic, indicated by slightly lopsided shoulders (Geralt's observation). Triss was burned very badly and magically healed but would "never wear anything with a low neckline in the future" (quote). And there were quite a lot more 'body flaws' described for several sorceresses which I don't remember in detail right now. Same goes for Ciri btw.: she's always described as very boyishly, has a disfiguring scar on the left side of her face and in general isn't exactly pictured beautiful in the books. The only sorceress I can remember that definitely was described as astonishingly beautiful is Francesca Findabir.
Sapkowski explicitly describing her that way indicates that sorceresses are not in general perfect, sexy models.
That seems to be a general video gaming trend though and sadly CDProjekt seems to be following it now, too. The trailer is amazing, don't get me wrong, but I think it's kinda sad that every character is starting to look more and more perfect - Geralt started as an ugly bastard (TW1) as described in the books and looks like George Clooney with scars in the new trailer. It's not a question of the graphics quality, the design has simply changed dramatically throughout the game, makeing him more and more handsome.
The trailer is still amazing and CDProjekt is creating great games - I just feeld that they'd be better if they wouldn't go for the pin-up character style and stay true to the books.
What you say is correct, but normal people would never be able to figure that out about Yenefer.
Also the change from a hunchback to a very beautiful woman is nothing to sneeze at.
The same goes for Triss, she was practically dead and disfigured, yet here she is, alive and kicking and very beautiful as well.
As for Ciri, she decides to leave the scar, even though she could easily have it fixed, to remind her of her foolishness and that she is vulnerable like everybody else.
Now to the point of the super models. Sorceresses may not be perfect, but they are head and shoulders above the normal people, thus they are extremely beautiful, even if Sapkovski's world.
To translate that to the current audience of the games, we all know what the standards for such things are in out society, ss such the game must provide the striking difference between the normal people and the sorceresses, but in a way that is plainly visible to the people that will play the game, all people, not just the hardcore fans.