You might want to roll forward in such a situation. You've gotta always mix it up.
And yeah his normals are boss compared to yours (c'mon arksys why you gotta follow murakumo moves)
In this matchup you've got to always keep your distance from him, which is pretty hard to do with his IAD. Often my 6a will clash with his j.2c and that just means he's automatically in.
Another thing about hakumen players is if you really get the scare on 'em (by baiting their drives and such) oftentimes they'll use drives in very unorthadox situations (lol it's what I did) trying to catch you off guard. I try to use more grabs because it'll beat out his counters, and even if he techs that leaves you at a neutral, midscreen position, which is much better than up close.
Also when you see him floating above you after a double jump, either just run to the other side or super jump into grab (especially if you've got 50 meter) Haku's very strong in the air horizontally, but vertically the only thing he's got is j.2c and j.B (still good, but pales to his j.c at horizontal power)
Also if you're in the corner try to get out however you can. His corner combo damage is 4k+ easily, even off of a poke like 2b. It's the worst place to be, seriously.
About using 6c to beat out 4c it's a great tool, but it'll totally get destroyed if haku decides to IAD. try to only do it if you have a stein to cover you.(2d/5d is pretty good)