Having the same problem as @bfieber, @sbstjn… upon stack update, I think it’s still hitting the PutMetricAlarm limit:
An error occurred: irhbackendTableScalingPolicyReadSponsorshipsDbThorndikeUseast1 - Unable to create alarms for scaling policy irhbackendTableScalingPolicyReadSponsorshipsDbThorndikeUseast1 due to reason: Rate exceeded (Service: AmazonCloudWatch; Status Code: 400; Error Code: Throttling; Request ID: dad4cc23-d376-11e7-842b-a3d7d952d5ce).
Looks like the dependencies you currently have are all logical dependencies … I think you need illogical dependencies, i.e. dependencies to the other scaling policies and scaleable targets being created simultaneously, because those are the ones that add up to the rate limit.