His debris throw really isn't that bad. Just stand near the building and slash away. He always throws one or two that require a vertical slash but you can sort of predict those anyway.
When he splits in half there's plenty of time to just block the sais, then the legs and throw your sai after.
My main issue with him was the smoke bombs. Sometimes he'd do it, sometimes he wouldn't. Eventually No Damaged him on Revengeance so 's'all good.
I've had where my swings would stop after slicing a vehicle, as if I'd hit a zandatsu spot. It only happened a few times, but it was enough to make me not want to risk it anymore.
There's time to block his long-distance sai and leg attacks, but I've had the legs somehow hit me on their third kick, even though I was blocking as fast as possible. Again, you can perfect parry the sai then block all the kicks, but after trying over and over to work out a strategy, it's not uncommon to want to minimize risk as much as possible.
If you lower his health to 70 percent after the fight starts, he will skip the smoke bomb phase. He will throw smoke if you don't parry his jumping spin kick (even if you block/dodge it). He'll continue the "throw stuff, land, attack" cycle until you get him to 40 percent. Then he'll throw the junk-wheel, followed by the long-arm/leg attacks.
If you're playing on Revengeance and you manage to hit him with a parry at the start, it'll drop him to 70 percent immediately. If you can get him close to the left side of the arena, he'll do that leaping-dive attack almost always, which can be parried and, if he hits the edge of the arena while leaping back, he can be hit with the counter attack.
I also found that he'll regularly do that leaping-dive if you engage blade mode. about 8 times out of 10, he'll do it, though he'll run around you for a bit. If you lock on, engage blade mode, exit blade mode as he's running and start it again, you can keep track of him until he does it.
You don't have to wait until you've blocked/parried everything before throwing the sai. You can do it straight after you finish blocking/parrying his first series of attacks. It's probably safer that way as well, since you don't have to deal with the legs.
Even if he's stunned, he'll keep doing those long-distance attacks. If you time it right, you can stun him, then block/parry those, but it's risky. I recommend, parrying/blocking the sai then running from the legs, then hitting him with the charged sai. I've always been able to outrun the legs, but sometimes the sai would hit me.