Ok... I can now get Armstrong under 100% consistently but there are two things that I just cannot reliably dodge:
1. The pillars of lava that curve towards you. I always seem to get caught at the bend so even if I dodge through it I still end up inside the lava.
2. His unblockable charge up and explode move. I just can't get the timing down to dodge through it each time and it's random when he does it so I can't always be far enough away for it to miss me.
And the amount of fucking times he does his fucking health recharge move right after he's knocked my fucking sword out of my fucking hands, YOU BASTARD ARMSTRONG. There's no way around that other than using blade mode on his back, right?
Christ, I haven't banged my head against a boss this much in ages.
On a positive note, this really helped:
Zep said:
...spamming Y+X+X(Spinning sword strike)
That definitely staggers Armstrong out of attacks more often than anything else I've tried.