DW AOE Rune of Rozorice help

[steelo]

During AOE as DW frost using rune of razorice is it beneficial to swap between targets and keep 5 stacks of Frost Vulnerability on 3-4 targets or even just 2 targets (for example heroic spirit kings or Stone Guards when 2 bosses are out at the same time) while still continuing my rotation and refresh them to 5 stacks when they are about to drop off.

What I would like to know:

Are they both dps loss?
Are they both a dps gain?
Is keeping it up on just 2 (in a heroic spirit kings or Stone Guards style fight) a dps gain but 3-4 (aoe fight) a dps loss?
Is keeping it up on 2 a dps loss but 3-4 a dps gain?

Any help is really appreciated, thanks.

[Vereesà]

Assuming all targets are debuffed accordingly and you don't lose white swings (due being out of range or whatnot) then there's no loss in DPS.