Damage probably needs a 10% nerf across the board. Possibly 15%. No reason champions with half a completed item can 100-0 in a single rotation. Also its not like it is just assassins doing this, tanks are practically to the point they can burst champions.
The damage creep even hit supports now to where not picking an assassin or burst mage support is practically trolling. Literally the least leveled least gold roll even wants to go full damage since its so powerful.
Its preseason, fix the game, bring back actual team fights.