Let's start with misery. If you really struggle with keeping your dots up, this can be a great quality of life improvement and higher dot up time will certainly help your dps. If you already have high dot up time (~99%), then you are just saving a few GCDs here and there. PI really pulls ahead by extending your voidform, where those higher stacks really start causing your dots to hit like a truck.
As for shadow crash, unless the targets are consistently stacked and you never miss, LotV is the way to go. Especially if you have the 4 piece. More voidforms equals more void bolts.