I've always found this argument to be silly. If I was an artist who drew nothing but naked women, would that be sexist? Maybe they're classy, maybe their not. What if a woman did it? What if I drew only nude men? What if I did that and was gay? It really doesn't matter. What if I liked cars a lot and drew nothing but cars? Artists draw what they enjoy drawing. Just because Hyung Tae Kim draws sexy, voluptuous women isn't sexist. IT can very well be (and this is an opinion I probably share with him) that he finds drawing such women to be REALLY FUN and visually pleasing. I'm a dude. I like boobs. I like excuses to draw boobs. I have another friend who just loves drawing muscles and finds whatever excuse he can to draw guys without shirts on. Or I have several female friends who draw porn for a living (or at least as an alternative source of income) and enjoy their work. A lot of artistic style comes from the fact that different people enjoy drawing different things and different kinds of lines. You can question an artist for having a limited amount of variety in their work, but drawing boobs is not inherently sexist. Hell, I'd be willing to argue that drawing tentical rape isn't inherently sexist either. You'd have to argue that having the fetish is inherently sexist. All the artist is doing in that case is visualizing their fetish physically. If someone draws nothing but sexy slaves, there might be a lot of correlation with sexism, but the act of making the art isn't inherently sexist. Maybe he's a sub with gender issues. Maybe the artist is a female who is venting what she thinks is some horrible desires? You can't know, and for the most part, it's not worth it to really care.
Now removing the artist from it, character design in a consumer product can definitely be inferred as sexist. Personally though I don't think the examples given are worth anything. DnD accepts a lot of impractical nonsense and a lot of 'rule of cool' stuff. You can say it's stupid and dumb, but that's different from sexist. What if it's all guys? It's still dumb for the same reason. Some series embrace this dumbness successfully. Many games and shows successfully pull off the hyper stylized aesthetic. Others 'keep it real'. If Caska in Berserk wore boob plate and had her underwear sticking out, I would find that terrible. It's out of place and is clearly not equal treatment. But in something where everyone looks ridiculous (for lack of a better example off the top of my head, lets say King of Fighters), it really doesn't bother me. One of the things I like about Dragon Crown's art is EVERYTHING is super crazy and silly, proportionally (well... besides the elf?).
On the other hand, what's the most famous example of a sexist character of late? Samus, in full on armor and everything. Sure you got the zero suit, but it has nothing on a lot of outfits. It's the character and the setting that makes the decisions with the character 'sexist' or not. Even if boob windows are somehow sexist, they are still far less egregious than a lot of other examples.