I am a katana fan, and I am not dissapointed at all. I understand your reasons to dislike the katana, and in fact you are right. But the thing is that a katana is a saber, not a sword, and it is not designed to parry with the guard. Well, no one sword is but the cross guard is more likely to give a better defensive ofenssive performance. However, the reason to this is that swords are more likely to use thrusts, while katana, and sabers in general, use a different setup of attacks, centered much more in the cutting power and killing in one blow. I have seen, by the way, the video you made about single blow kill, and meanwhile it is all true, I find that is not true that didn't exist one killing blows, specially with sabers that leaded more to a clean cut than to a chop. But, for this reason, the katana is played in a different way than any other blade. The katana is used with counterattacks. I mean that you first parry the hit, but more than a parry, what you do is to hit the opposing blade to change the direction of the blow, then you hit leaving your defense open, but you don't care since you have already broke enemy's defense and he is left to a brutal attack. Even if you don't kill him in a single blow, you are supposed to recover your defensive stance before he can attack you again, since katanas have a better mobility due to the graviti center being closer to the hilt. It is simply a different way of fighting. The longsword, for example, leads more to kill the enemy by bleeding AND exhausting the oponent, and the fighting style centers in winning the advantage over your enemy till you can finally kill him. You never leave yourself open. Katana is supposed to cut the flesh, but actually looses most of his potential versus an armored enemy since you can't really cut through metal and delivering a killing blow at the same time. Swords can't neither, but they have the advantage of being more adecuate to thrust through the weak points of armor, due to the non-curve shape. Is easier to be accurate when thrusting with a sword. In fact, in the japanese wars, the katana was not very used as a main weapon, not at least versus the generals, but agains the peasant's troops that lacked armor. Versus armored enemies, they were more likely to use tetsubos or other weapons that gave better performance versus an armor. The katana was more of a symbol than a true war weapon. He gained his fame during the Edo period, during the Tokugawa dinasty, due to the ammounts of duels and skirmishes fought during that period. Summing it up and making an equivalence to fire weapons, katana was more of a police weapon like a pistol is, and swords, maces, etc., were more of militar weapons as an assault rifle is.
That's my opinion at least. If I am wrong with something, I would appreciate to be replied and corrected.