Yoshi sucks against a Mario with cape or anyone who can knock him back after his jump is over. It really hurts him a lot in hard core tournament play. And Pichu would still suck even if he didn't hurt himself... he relies on items. If you got tournaments to allow items, he'd be good. But tournament players are really stupid like that. For that same reason though, Ness's situationally bad third jump doesn't matter. The only thing you have to worry about are players who love to jump into your PK thunder while you are trying to recover.
What Ness has... is style. You can set up a yo yo glitch once you figure it out and grab your opponent from the entire length of Final Destination away. Or the third jump attack as well. Or you can get extra stylish with it and use the yo yo to launch the opponent then use a dair jacket install off of the glitch so that if the opponent touches you at all its automatically in a very comboable situation. Of you could install a pk thunder jacket to make a huge fraction of melee attacks against Ness result in 3rd jump damage against the attacker. There are other options with it as well... but generally, the yo yo glitch is as sweet as all hell.