Dom+Inspiration is becoming standard on burst mages. Though all my thoughts on runes aren't solely based on the stats and are more influenced by testing, look at wrs for Vlad, Fiddle, Teemo, etc. This is consistent across burst mages. With the damage nerfs, Dark Harvest is necessary to compensate.

Inspiration second is also becoming standard as a good go-to default secondary. Boots+Cosmic/Biscuit gives a lot of value+sustain. This is also reflected in wrs. The secondary landscape right now is 1) footwear+biscuit as default, 2) taste+hunter branch for long range, low cd abusers, 3) triumph+tenacity for Resolve primary tanks, and 4) two from Resolve for AD conquerors. Gathering storm is always a gamble; with 9.10 changes it'll be good enough to enter the above ranks as a hedge against getting outscaled.

Lastly, Dom+Inspiration is Karthus' best runeset, with DH being the best dmg rune for him and footwear+cosmic value being way too good.