They did change the regeneration feat in the latest update. I don't know why since I've never had an issue with the feat before. It was only the Warlord who has a passive 25% damage reduction and an extra +35HP that could truly exploit it.
Not quite sure how it works since the change. What I have noticed though, is that if you're using Shugoki's Throw Farther feat, it stops the regeneration feat from working. You have to use Speed Revive or Iron Lungs instead.