Three trees dedicated to damage, and no Spell DPS Keystone?
Nearly every keystone from the existing system has some kind of parallel in the new Runes system, or at least something that fulfills a similar purpose. The sole exception is Deathfire Touch, which was the keystone which explicitly catered to Spell DPS and/or DOT based champions like Malzahar, Karthus, and Swain.
That's not to say there are no options in the new system for those champions (though the TLD and Stormraider's parallels have been directly nerfed for DOT champions). It's just there is no option that is a direct "I want to have absurd DPS" for them the way Press The Attack functions for ADCs.
is throwing rocks across the map everytime you step on a shroom kappa.