So in regards to runes:

1. They're strong.
2. You can realistically only get 4 star ones from the boss fights.
3. You share the progress and the bosses with your guild it seems.
4. The point of the option to reset to lvl 3 or 6, and the fact it costs more gems than resetting everything, it's all because of the ability to reroll random effects
5. They can contain some previously uber rare effects:

Movement speed increase/rage recovery/pierce/crit damage - random effects
Crit Damage increase 30% - Yellow set effect
Healing 8% - Blue set
Def 4% - Brown set
Pierce 15% - Red Set

There's even:
Atk 8% - green
Atk 4% - red


5. What this means is that it's now possible to make a crit build with an assault unit. 180% crit dmg. Make tanks that are quite tanky, and Healers that heal for almost 50% more.

Or rather, you can get 90% pierce. If pierce is what it sounds like, and ignores enemy defense, then doesn't this obliterate tanks?

And if you can find a (very rare) crit rate hero, such as Prundroestris (an 18 quality fusion) with the perish skill (increase crit rate 20% when 60% hp or less) then you can make a crazy crit build. Traditionally in rpgs, this kind of thing breakes the game. Misuki increasis crit rate by 35%...