Response to Reviewer

"...Provide some evidence that the parameterizations relate to structural properties of failure graphs arising from real There are many application scenarios where our parameterizations are reasonable. "Analyze the complexity of these problems in the more common scenarios 1, 2, and 3. Do the problems remain NP-hard We will add a specific remark about the above into the final version. "the paper said that it would use a spade to mark statements with omitted proofs, but they were not actually marked with We apologize for this confusion. We will fix this in the final version. "It might be helpful to add a chart to the introduction, indicating the map from parameter to tractable/intractable" Thank you for this suggestion.