I think there should be restrictions on the amount of runes one can put on a hero. Everyone uses the same runes at some point in time. It would be more strategic if you could have MAX 4 runes in my opinion. People would have more weaknesses and some runes would end up being more effective as you wouldn't be able to counter them all. Right now it's merely a race to get as many high runes as fast as possible, and to level them as fast as possible. A well chosen block would be much more effective if every hero did not have break, for instance.

Now, runes as they are are merely an incentive to grow as fast as possible, because reaching another 10 levels means putting one more rune on each hero, which is a tremendous advantage.

The question is, do you want to make the game more strategic or more like a race to the finish?