After a million attempts at OoK I'm calling it quits. I just can't do it. Every boss I can down, but the margin of error on OoK is way too low for me and the speed on him during 2nd phase is ridiculous and beyond my skill.
I just beat him with my Rakuyo, took me 3 tries. I found that dodging toward him really helps, but you have to also make sure you aren't directly behind because some of his attacks swing back behind him. If you get enough hits in, you can stagger him, it probably took about 6 hits for me to get him to stumble a bit. Whipping out the lightning paper or the empty phantasm shell also helps. During the second phase, when he jumps up and is about to stomp me, I wait a moment, then roll towards where he was, then I can get a hit or 2 in. In general, I found that being close (but at least far enough to side step attacks) felt more safe than farther away, because he wouldn't throw as much crap, he is less likely to leap, and it allows me to be in range to land hits which will eventually stagger him.
On another note, I think Rakuyo and Beast Saif are replacing my burial blade. I freaking love these weapons, and they both feel good against other hunters (L2 in transformed Rakuyo has hyper armor on some frames, and it can hit twice). Beast Saif absolutely wrecked
, it took me 4 tries because of the 2nd phase and I was using burial blade, but then on the 4th attempt I just used Beast Saif and stunlocked with some gunshots to the face for viscerals. Now I just need to beat the secret boss to get all the achievements for the dlc.