I have simple idea.

Some people want it easier so you can spend more coins faster
some want it left alone.

How about this.

There WAS/IS a red run called synergia or something like that which gives 1200 exp to any rune. I dont know if this rune still exists. It was reported with a screen shot once in the past 9 months

BUt i think if the final rune keeper only gave out
1.synergia
2.frags
3.purple runes
4 gold runes

NO blue or green runes

Then that could speed up leveling a rune with out making any significant changes to the way things are