i think the main the reason is not from the items, so what if you have items but you cannot deal damage, lots of champions can jump on AD carries and burst them down, examples are assassins, it is about the teamfight, it is about can the front line hold well enough, can support protect good enough therefore twitch but be able to play in tourn but varus' chances are pretty small, the fact that he doesn't have escape and carries without escape usually are hard carries such as kogmaw but varus is not as hard as that so ya.