I have had some brood mortality in the past, but never enough to worry about. I have also seen queens that shut down during treatment. When I go in after 7 days to remove the pads (more to check than actually needing to) I have found fresh eggs and capped pupae, but missing degrees of larvae.
This year it got very hot, close to maximum temps when I already had the strips in a bunch of hives so I am a little concerned. I held off doing anymore until the temps finally dropped today.
I have always placed a super on top during treatment, it wasn't in the initial instructions, but was a recommendation in the early days of the product I believe.