When I read on the patch notes that unbreakable shield would be able to last longer the more enemies shot at it in was exited but when I tested it on my prismatic titan with spirit of the bear on my exotic titan mark, I was disappointed to find that tho the icon does reflect the damage taken refills your granade icon witch usually = longer duration for your shield, I found that it would end on the same time as if no enemies where dieting at it. It works on pure void titan just fine. It's only on prismatic that it does not work.