Why is DRK so squishy and how do I stop it?

[Seku]

I'd be curious to compare shield blocks versus the passive -20% at that level. Say on an average, you block around 20% damage. Would that not, in essence, be equal? You're almost constantly blocking stuff, depending on type of shield you have as a PLD. So in that regard, I would think it would be awfully close and when PLD hits 40, that's when they become the better constant damage mitigator...

No, because shield does not always block and does not proct even 50% of the time. Grit is -20% damage taken to everything and will always work expect if the damage is mechanic damage (like falling to your death in titan, hitting a flame wall in coils, hitting enrage on bosses ect.). When they (PLD) hit 40, then yes they are arguably the better mitigation tank.

I didn't have full calvary. I had HQ Toadskin pants that are for tanks because I never got calvary pants to drop

Then the defense missing would have been around 15-20 roughly. Which can make a difference, but in the situation you were in, single group pulling from the sounds of it, it's not that big of a deal.