Not really a bug but an annoying thing.
Talking about "Survival Mode", Old Axe Armor is too powerful and fast. Mostly when it does that "many axes that follow you, block you and kill you" attack. It would be cool if its damage, defense and that following axes attack time or speed were reduced. I went on winning sprees of even 80 victories, all interrupted by that basterd.
Another annoying character to play against in Survival is Yoko Belnades. She always does that "Holy Lighting" attack. It doesn't do much damage, but when she does it a million times it's lethal and annoying.
That's all for now. I hope you'll think about these two a-holes.