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

[Sarcatica]

Actually, that does make a pretty big difference, especially on trash.

Pld's low enmity gen practically forces them to rotate RoH to maintain hate on trash mobs, unlike War and Drk who can pop a couple of Overpower/Unleash and be green as grass. A good Pld will make sure that their rotation targets as well, so the RoH debuff gets spread around. At 20 seconds per debuff, roughly 3-4 targets can be inflicted with a physical damage reduction during (varying on skill speed, personal skill, and lost time caused by extending circumstances) on top of blinds caused by Flash and whatever mitigation skills the Pld has active at the moment.

Now, the debuff itself wouldn't normally be all that great because it only effects physical dmg, but the vast majority of trash mob attacks are physical (including auto attacks). Magic wielding enemies are actually quite rare by comparison. In most dungeons, you're roughly looking at about 1 in every 3 enemies who use magic as opposed to physical, and even then, some of them still have a physical auto attacks that can be mitigated. Individually, it's not much, but it adds up pretty quickly and scales with the size of the pull.

It's not as terrible as you actually point out. For what it is worth, let's just say that -10% STR = -10% damage taken, I doubt it but for easy calculation put it at 10%.

Let's say total HP is 3k. Each hit will do 300 damage per mob, 3 mobs = 900 damage. -10%STR = 810 damage. 1 cure is enough to top someone to full. It's even more trivial if you use CD since they aren't additive.

TLDR: Rage of Halone is not going to matter that much for fluff damage (autos mostly), difference is if you are getting physical tank buster, then RoH is great to mitigate spike damage.