There are two good strategies, IMO.
One: Stand still on the first platform, use charged slash attacks when the orb gets low and use cross tanks like there's no tomorrow.
Two: Position yourself on the upper platform, charge your sword, jump down and slash, keep doing charged slashes while avoiding projectiles (without running). When you have to dodge to the right, climb up and repeat. There's usually an opening where you can fairly easily jump down without getting hit.
The trick in the second strategy is that charged slashes tend to erase the crosses coming at you, so you only need to dodge the split projectiles. Of course, some crosses will eventually get through, which is why climbing up again is often necessary.
I prefer the second method, as it's cleaner and faster. It's quite risk-free once you get it down, too.
I've seen replays where someone charged towards the Wall from the upper platform and does a dash jump slash and repeats that, but I find it awfully difficult and slow way to beat the Wall.