I think Marth's saving grace is the fact that Ike hasn't ganked any of his moves, as near as we can tell (eruption is somewhat close to Marth's shield breaker, but his Up+B definitely isn't). Also, Ike is a heavy character and is a great deal slower than Marth.
Lucas just has most of Ness' signature moves, especially the PK thunder self-inflicted recovery which was Ness' trademark, if you ask me. If Lucas' forward smash is a bat, then I think it's safe to say it's game over for Ness (at least except as an alt costume for Lucas).