Nice I use Arthur too! Got any good arthur tech? I've been experimenting with super jumping into jump S and immediately canceling j. S into his projectile specials. Doing this with knives kinda reminds me of a short hop laser lol. He can launch 3 times in the corner too, it's funny. I'm also one of those crazy people who runs arthur on point instead of anchor.
This is all I know about Arthur. Golden armor is only good for x-factor level 3, and using him as an assist in preparation for x-factor level 3 arthur. Otherwise it is just not worth the bars and the HARD KNOCKDOWN state you will eventually be put into. That being said Arthurs jumping S is amazing. Because of how quickly he can do a jump and quickly do is j.S he can do some very scary instant overheads for opening people up. if you can get into the habit of doing quick hops into J.S. you can almost do something like a pseudo tri-jump in the way that you can get mixups. The instant overhead scares them into blocking high, however the shenanigans come into play when he is on the ground because he can still attack low. Either way you can get a full combo off of a hit. The j.S is also pretty safe on block so it is hard to punish. Naturally your opponent is going to try to pushblock you away, but that does not mean much when you have the long range tools Arthur has.
My gameplan is pretty much play a normal game with my other 2 characters and much sure I at least have 1 bar for Arthur. Once he comes in I do my level 3 x-factor nonsense, although powered up or not his dagger assist works well with Chris and the other characters i use for the first 2 slots.
Towards the end of vanilla people used to just counter with their own x-factor and turtle out my Arthur, but this is no longer the case with his new j.S. Combine that with x-factor speed boosts and arthur can become pretty damn scary. If they choose to turtle me I can superjump and do j.S for a crossup or a high low mixup when I land. If they choose to attack then I will almost certainly catch them with his lance infinite/block stun infinite.
My main goal is to do as much damage as possible with the other two characters to make Arthurs job easier when it comes to him. I am still working on how to handle aircampers since they negate his high/low mixup game. So far I just chase them down with homing arrows and try to force a mistake.