Paladins are - I want to say - the tank with the most active defense necessities. If you aren't using at least reprisal and rampart (and sentinel during emergencies) regularly, you're going to take way more damage than other tanks in equivalent situations. Shelltron should always be up, and you should be dropping occasional heals via clemency as needed.

Honestly, Paladins have an easy rotation, but they're really demanding of a tank to pay attention to damage spikes, making them somewhat unforgiving if you're just hoping to faceroll all content.