If they have grit up they literally only take about 5% more than a PLD does...and with Dark Dance (esp DA buffed) up they take significantly less damage (though prone to bursts).

Their cooldowns are almost identical to a paladins.

The rest may simply be

1. Gear. Leveling gear varies wildly. Simply upgrading my gear from lvl 52 to lvl 55 gear made me take 20-30% less damage.
2. Confirmation bias. You're used to assuming they're squishier.