There's only so much you can do for a set that mainly relies on one form of survivability. It does have that scaling resist based on missing HP, but I am unfamiliar with how well that gives your character time to recover from actually getting hit. One of the reasons I prefer Inv is because it has many layers of mitigation - capped HP, Defense, Resist. Add in DM and you've got a constant heal, soft CC, and plenty of -ToHit. I like taking Shadow Meld and Moonbeam with my DM/Inv. The quicksnipe does good damage, and Shadow Meld adds a large amount of Defense on a quick recharge to help reset the -Defense that does go through. Mine is currently 15s duration with ~30s recharge, so it can be used quite often as a form of protection from -Defense.