Looking at zirc's new list, I think that swiftblade and magebane should both drop a tier, while Valkyrie should move up one tier. Swift is probably the best firstblood char in the game -- but his utility is relatively limited in teamfights, and eventually (around 15) his whirl does LESS damage than his regular attack.
Magebane will deserve the spot after the next patch (he's being redone), but currently his high movespeed is the only thing keeping him relevant.
Valk needs to be one tier higher because not only is she relevant for the entire game (rare among the cast), she excels at the vast majority of it. Her leap ability scales very well, giving your entire team the equivalent of Slash's extra damage and movespeed for free...and her arrow allows her to help gank from half a lane away.
Finally, I can't decide which tier they belong in (probably , but both Zephyr and Wildsoul should be in the same tier group, as their playstyle is VERY similar -- farm Mock ASAP, then destroy the team before any high DPS carries get their stuff.