Plane Sailing
Astral Admin - Mwahahaha!
If you were going to do straight out damage, I'd actually expect it to be more like x1.5, fwiw - it's 45% chance of failure base, often 40% or even 35% - 20% for dwarves against poison, and damage is more valuable up front than lingering in a way that doesn't stack.
As I said earlier, the actual figures are pretty close to: normals would receive ongoing value + 80%, elites ongoing value + 50% and solos ongoing value + 20% (I just put the figures into a spreadsheet with appropriate save percentages, accumulating the expected damage over 6 rounds or so in each case (which brought it down to just a few %age points by then in all cases).
Cheers