>>So, it does contain a training arc.
If by "arc" you mean three chapters, one of which is actually almost entirely focused on something that's happening elsewhere, then yes, I guess it is. Not to mention that, had you actually paid any attention to something other than "lol, he's trying to become stronger", you'd notice the purpose of the trip had nothing to do with strength, he was trying to learn how to control himself, ehich he linked with his incomplete knowledge of his art. Kenshin's bigger problem throughout the series isn't winning, it's winning without going insane.
-leader of the oniwaban
Aoshi. Is that what you call "getting fucked"? His "hax" there was making use of the delay in his attack and grasping his sword with his hands, which was something he figured Aoshi wouldn't predict because of his style.
-former shinsengumi leader
I suppose you mean Saito. The battle was completely balanced all around until they were interrupted. There was no way to know which one would win.
-the kid with no emotions
What the hell do you mean? Kenshin even had the luxury of shit-talking him as he was bouncing his attacks, until they both ended it with his final move.
-and, of course, shishio.
Once again, everyone else jumping in can't be called "hax". Sure, he would have gotten killed otherwise, but you have to count Shishio was fresh and knew about his techniques while Kenshin was just out of two fights and knew shit about his. You know, the whole "feeding" thing.