FireHydrant can make changes to an incident in a single runbook step.
Add an 'Incident Impact' Runbook step
To set up the Runbook step, select the Incident Update step from the dropdown on the Edit Runbook page.
You'll see a couple different options for incident updates in this step.
This step should allow you to automatically update severity and priority as well as update the description and customer impact. All of these changes can have a note accompanying them as well.