too much dair. It's way too predictable and slow, with very little priority (at least for me it has little priority). too much of a running approach, which caused several trips. rather than running, SH some aerials while moving towards him (listed in order of what i recommend: fair>fair (for spacing and to ensure at least one hit)/ fair>(nair, if fair was done immediately as you jumped and the enemy is kept close)/ nair>nair/ bair>nair (i can almost always sweetspot the bair, even when the enemy is in front of me)). I really like the ability to SH two aerials with ness. big characters are pwned by pk fire, especially bowser. tried too much to do mindgames with pkt, which leaves you wide open if the other person is smart enough to dodge it. I like the yo-yo, but sometimes it's not the best option (charge when expecting them to shield, perfect usmash and dsmash so you don't need to turn around all the time for the yo-yo). I'm not a pro or anything, but this is what i suggest for him. my play-style is a bit weird in actuality.
Other than that, good grabs (i cant pivot grab ever), good jabs... well he's not terrible, he's just gotta work out a few kinks in approaches, combo more often with dthrow, and use pkt less than pk flash or CAZCOMBO! when the opponent is off the stage.