Orochimaru was seeking the Totsuka for years before Itachi showed he had it.
Why? Was he looking for it so he could use it when he had an Uchiha body? MAYBE. Or Perhaps the blade is compatible with his Eight Branches technique somehow since regurgitating blades is his thing. WHO KNOWS?
It's not clear, i.e. there's no concrete evidence the Totsuka is exclusive to the Uchiha or Susanoo.
"At the highest level possible" uh no... kitsuchi solos in doton, kakashi and Darui solo in Raiton... Danzo and Naruto solos in Fuuton... Madara solos in Katon... tobirama and Kisame solo in Siuton...TenTen solo in Bakijutu, Itachi solo in Genjutsu, Minato solo in FuinJutsu... come again?
he master the villiages jutsu not ALL JUTSU you are wrong otherwise he would low diff the WEAK VERSION of Tobirama and Hashirama he fought without damn suicide
Hiruzen doing something at the highest level doesn't mean there are others that can't do it better, i.e. Hiruzen may have mastered all the elements but others may have mastered better than he has, but lol at some of those examples.
Kishimoto has stated in no uncertain terms that Hiruzen, in his prime, was the strongest Hokage Konoha has ever had. What does this mean in terms of his combat ability? I don't know, maybe his element combo jutsu were even crazier back in the day then when they were as an old man. It doesn't really matter. We just know he was that strong because we've been told so by the author, whose word is law and irrefutable.
In other words, deal with it.