ok first of all, mario party 8 is a party game, and you can't have a tier list for a party game. that game is ***** gay as ***, the whole time you're just wackin off with the wiimote.
2nd of all, yoshi is not bottom tier. wtf is wrong with you guys. Wario and DK are fat as *** and get hit by everything in the minigames and have a horrible map game. yoshi also has decent map control and gets good items at item shops. however, because of Yoshi's awkward shape, he is low tier. Dk and Wario are bottom tier.
mario is also slightly better than luigi. luigi definitely is better at the minigames, but mario ***** at getting items. He gets the best items out of anyone in the game, so he is better than luigi, but still lower than waluigi because waluigi is broke as ***.
the main problem with your tier list is that it's based around minigames, but mario party 4 has other elements to it such as map control, item control, etc. that's about it.