Atziri's Rule Flames of Judgement problem

Flames of Judgement : Creates markers at your location and a targeted location, ""which grow over time based on cast speed"", then explode, dealing fire damage. Cannot be supported by Spell Cascade.


I used faster casting support and cast speed ring, but the marker whether area or grow speed are not change, and I tried acceleration shirne too but still same.(I know shrine is increase action speed)

is it a bug?