As the title states, LoL likes to make champions one-shot everything. IMO, it would be best to reduce all champion stats by 30% (or a number the community sees fit), except for HP and mana .
The ratio's will remain the same, so nothing becomes stronger or weaker. Just as long as all stats are equally reduced (except for HP and mana ofcourse), the balance (ratio) will remain the same as it now is, but just less one-shot potential in general.
For the people who won't comprehend what I'm saying:
Let's say all champions have 100 AD and 100 Armor (fictive numbers, but to get the point accross). After they reduced it by 30%, all champion will have 70 AD and 70 Armor.
Or... you don't have a problem with One Shot Legends (or League of One Shotting :-D).