It would be cool if there was a unique bonus for every rune path combination.

In others words having there be a unique thematic bonus for each of the those named combos such as "The Aether Blade" (Domination + Sorcery), instead of the boring health/attack speed/damage bonuses that are the same no matter which secondary rune tree you have save for if you have inspiration as primary.

For example, the aether blade would get some magic damage on hit as a bonus or anything that would fit the name and theme of the combo. I think that would make runes a lot more fun to play around with.