The problem with the new rune system:

Is it promotes chasing kills instead of safe farming. Now there is a rune that gives you +25 gold for each kill/assist and another rune that grants ad/ap based on your takedowns (it also works on ward kills). It is worth about 42 gold per takedown. This makes the game even more snowbally because the person who is behind can't reap the benefits from this rune. So now instead of kills being worth 300 gold, they are worth 367 gold if you take these 2 runes, which every assassin takes. This also makes champions that have low killing potential early game, like tanks and late game champions, at a big disadvantage because they can't keep up with the carries.