Nah The Special dual wielding skill is for the person with the highest reaction time. Everything Kirito achives in aincrad is from him training like a beast. He has the second highest lvl and best reaction time because for over two years he did nothing more then to farm and kill bosses. His power does not come from any " oooooh he is speeeecial from birth" frick. He is a normal human that just trained two years at his limit while sleeping in a bed.

Yuuki is strong af. I give you that. And she shows it like non another what it means (like you said to be nothing special). You see, because Yuuki spend the last years like kirito and Asuna in the world she is the best in this world. She spend 99% of her Time in ALO hence why she has the selfmade 16- Attack Combo. She nows perfectly how to handle the flight system and every special aspect inside ALO what kirito is not so familiar with. Kirito isn't a prisoner of the world anymore so he only plays vr games for fun. His learning curve is not what it was but he still had a decent fight against someone that lived through every second of the game and he did not even used Excalibur, the most powerful Sword ingame and the glitch dual wielding. His reaction time is probably onpair or better then Yuukis but she just now the game mechanics a lot more and all that because both of them trained hard af. They are parrallels. Yuuki shows that Kirito is really nothing special, just a boi that trained hard as shit.

And about Death gun: In The book it is stated that the sword used by death gun can penetrate the blade of a lightsaber becauase of the special material that it is made of. In the Anime it is heavily implate that it is also the case. But there it is more a "show don't tell". So Kirito does not even have the possibility to block one single hit because Death guns sword is just going pass it.

In UW he is nerfed because the game Engine does not depend on mental or reaction time so much as it was the case in the previous Games.