Yoshi is really good if you know how to use him right, not many people see it but his Up+B is somewhat his 3rd jump, so he's pretty much set this time around, he wasn't as good in Melee.
But they gave him a very good upgrade, plus it is fun to kick people's arse with em'!

Low Tier or worst blah blah, don't care... either way, I think Yoshi is probably one of the better ones, not many seem to notice.