I really like the design Larian did, they are incredible. And I'm in favor of sexual demorphism.
First, about the ''realism'', don't forget that lighter amor were used in history. Romans soldier had naked legs, and Celtic warrior could be bare chested, or bare legged. Not everyone is in full plate armor. Actually, full plate make you really slow and is quite heavy. Its makes senses to have lighter part in an armor and to protect only place like shoulder, knee, elbows and hands. The more full ''armored'' you are , the slower you are.
And yes, revealing armor are usually sexier, can be more charismatic and have more personality than bland ''full covered armor''. Body shape are dynamics and beautiful by essence, and merging the mecanical parts of the armor with the organic part of the human anatomy can be pretty and aesthetic, IMHO.
Not to mention that, male armor DO follow male chest, which is flatter by nature. Breastplate armor of fantasy woman follow the curve of the chest, but so does male armor, so its not sexist or anything, same concept.
And as Scribe mentioned, this kind of design has been there like forever, because its pleasing, aesthetic, sexy, and to some degree, historically grounded (not talking about the chest metal plate which I have never seen, but revealing and half naked armors are part of history and many cultures).
So yeah, I think we shouldn't be too judgemental of that and just enjoy the visual.
If it's what it's takes to save the world, then the world doesn't deserves to be saved - Geralt