I know blurs are still new to inkscape but I was wondering: Is there a way to stop a blur from leaking out of a path boarder? Some times I want a blur to over lap with another path's fill, other times I don't. I'm been using Dynamic Offset to minimize the over lap but that has it's limits.

I don't really understand the question, but note that the way blur works now is how it will always work (despite still being "new"). So you may need to find a work around for the effect you want.

Perhaps you are looking to clip the blur?