After playing around with Joker for a good bit, I feel that he honestly is pretty damn solid in general. While he has his clear flaws, I see a lot of potential. When I look at Joker, I see two characters I would compare him to: Sheik and Greninja.
In terms of movement, Joker is pretty fast and has a very low run. This helps as he is a tall and growing boy. I could see dashing as being super important to his gameplay as a result. The gun sliding also is pretty damn solid as well, and makes triplats and any stage with decent platforms very goood for Joker. I can see Joker's striking FD often due to this, so I can see Kalos or PS being the main counterpicks against him. Compared to Plant, Joker is much more reliant on stage choice in a good way. If this wavebounce ability is used to its full extent, taking Joker to a triplat is askin for a bruising.
To me the real killer tool in Joker's kit is his up air. Yeah yeah everyone talks about how his up air is good. But it helps him out so so much. It has a good hitbox, its fast, it deals decent damage, its easy to get into, and drag downs. Oh my lord drag downs. Drag down F Smash will be the key tool for Joker to try and kill aside from fishing for back airs or edgeguarding.
Speaking of which, edgeguarding. His down air has a great semi spike angle. You might use this for trying to go for a grab combo of some sort, but that semi spike will be pretty solid at edgeguarding too. Granted you have to deal with Joker's mediocre recovery to edgeguard sometimes but its a good risk. Also, lets not forget the value of the gun down, which will be solid for just messing with recoveries.
One thing I feel is getting overlooked is Rebel's Guard. Now generally Counters are kind of bad in Smash. For real, unless it is Witch Time, counters do not do much outside of just helping gimp Chrom. However, I feel confident in saying that Rebel's Guard use can just turn Joker into a far better character. Wise use of Rebel's Guard can make it so you can get Arsene out twice rather than once a stock. This is crazy good for Joker as it essentially multiplies his damage output so much it is ridiculous. Now I know counters in general are unreliable, but I would not hesistate to say overall this is probably the second best counter in the game after maybe Witch Time
Joker has his problems, such as mediocre range, poor recovery, and other things, but I see so much potential with this character. I expect him once figured out to be High Tier at least, and I can say I am putting a lot of effort into maining him alongside Ridley.
In terms of the patch, Mewtwo and Corrin look better, especially with Mewtwo no longer getting tail sniped as much. Mega Man is not happy with the huge nerf to projectiles across the board. I expect some experimentation with these two, though I do not think either will instantly become a tournament threat.