*sigh*
Ike is better then Yoshi. And Ness. And arguably Mario. Ike has the tournament results on all three of them by a long shot. Ike has gotten his first First place finish and second place finish since the last tier list, as well as a respectable load of top 4 and top 8 finishes. He's moved up above Luigi for sure and most likely Toon Link in overall tournament results. Ike's abilities have grown a fair bit since the last tier list, and those new findings also improve his match-ups against various characters. [27 grab releases on 21 tested character. DACIT against any character that has throwable items (Link, Toon Link, Peach, Wario, Diddy Kong, or against anyone at Distant Planet or Green Greens).]
Ike has done enough to keep his mid-tier spot. Particularly against those 3. While admittedly I don't poke around the Ness or Yoshi boards as much as some boards, I haven't seen anything that suddenly stood out. Unless I see something I've missed since I've last checked those boards (which I'll look for after this post), Ness and Ike should switch spots for sure, and probably Ike > Mario. I agree with Yoshi's spot of top of low, heck, I could see Yoshi being above both Mario and Ness, but Ness and Mario just look out of place.
/endbiasrant
EDIT: With further digging around, I believe for sure that Yoshi>Ness. Not sure about Yoshi VS Mario yet