Gotta cast that Ruin II when tank chain pulls 9 mobs, it's sure as hell going to make a lot of difference (actually no, you are being inefficient and losing out on a lot of DPS). An outburst with the ruination effect hitting say 5 mobs accounts for 450 potency. You don't want to waste an entire GCD that could be doing 450 potency for one that will do 180 potency just so that you can weave your painflares or EAs. But whatever, you can keep casting your Ruin IIs against 5+ mobs.