First, you should not add indexes simply based on the missing index DMV. It will give you bogus duplicate indexes based your queries, and requires knowledge to properly create indexes.
Second, those indexes may include the same field, but they are not the same, If you create an index on [camp_id],[open_time] that index will likely not be used when you query for [camp_id],[submit_time].
I suggest you use a method of ranking the suggestions, and evaluating the top 10 results. Then try again in a month or two and see the top 10 again.