We have an abundance of mitigation tools (especially Reprisal being 30s). Succor is effectively equivalent to a -10% mitigation button in terms of mitigating one instance of big damage and it costs 1 gcd.

Squeenix gave us a ton of free mitigation tools, but is afraid to force us to use them. At the moment, they mostly serve as a tool to trivialize fights.

If they're afraid to make us wipe because a Reprisal is missing, I have trouble believing they will make us wipe because of a missed Succor.