I appreciate your post is fairly old - nevertheless we had the same "out of office" problems that you describe.
As a Marketplace Vendor, we ended up building out own Plugin, which we have just released to the public:
If you are still looking for a solution, maybe it's with a look.
First, I would like to confirm whether my understanding is correct or not.
Imagine, you being a Assignee of an issue, you may get notified for all updates on the ticket. While you are out of office, you would like to set an auto generated reply for out of office. Am I right?
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event