Instead of giving users access to Case Feed through permission sets, you can create a custom profile that includes the Use Case Feed user permission.
|Available in: Salesforce Classic|
|Available in: Enterprise, Performance, Unlimited, and Developer Editions|
|To create and edit profiles:||“Manage Profiles and Permission Sets”|
The Use Case Feed permission is available only on orgs created before Winter ‘14 that haven’t enabled feed-based layouts. Case Feed is automatically enabled and assigned to all standard profiles in Salesforce organizations created after the Winter ’14 release.
- Create a profile.
- On the Profile page, click Edit.
- In General User Permissions, select Use Case Feed.
- Click Save.
- Assign users to the profile.