@hero_swe: That was also the only boss fight I died on when I replayed it last week. I played it through on a Vita and didn't really have an issue with it at all. Actually the first time because lunge is mapped to square, I tried to only use that attack so I didn't have to use the terrible Vita sticks but it did so little damage I just couldn't kill him faster than he could kill me.
But second time I just used the sticks and found it SUPER easy... once you learn his attack pattern it's not really that difficult at all... tbh I found the Fatman boss fight the most stressful and the Vamp fight the least stressful (lol grenade launcher)...
His pattern wasn't the problem. It was the fact that for some reason everytime Raiden swung his sword he would start spinning in some direction, so if you tried to do a basic 3 hit combo. You'd be facing 90 degrees away from the direction either side of the way you started. Always ended up facing away from solidus which meant I only either got two hits in on him or he parried two and then just hit me while I was stuck in animation on the third swing.
I also beat him eventually, only took about 3 more tries just doing single swings and patience. What baffles me still is that I used the sword before that point and he never did it there, it must be some corrolation between the "dynamic" camera.
I think it was maybe the way you where using the stick? If you did a circle motion with the stick he would spin around, so maybe it was that? Using the Vita I simply mashed at the right stick when ever I got a chance and second time I breezed through it np and never had him spin round, though that could just be because the Vita's sticks are garbage.
But from a narrative point of view I do really like the move to fight the end boss with a sword.