Higher Tier Items

Have you noticed that when you are ahead in kills and you are carrying for your team, which are feeding, how you reach a certain point when you buy your full item set and there is no point in farming anymore? And as the game progresses you become less and less useful. I think there should be an even higher tier on certain items. And so that the game is balanced there should be some restrictions to buying these higher tiers of your items. Restrictions like levels or maybe they just cost a lot of gold. Or maybe there should be more powerful elixirs. What do you think guys?