Simplicity over complexity, time to change.

[Zumi]

What if you are fighting something that does a lot of unavoidable AoE damage but isn't made any easier by high DPS, wouldn't you like the option of using a higher defense/HP set at the cost of DPS output?

This already exists in the form of melded accessories. You can be a dps say a monk and have melded accessories with vit, str, crit/det, you sacrifice some str for vit. Almost no dps does this because they don't care about survivability as a dps, because most dps think if they die to AoE its the healers fault. There is a lot of unavoidable aoe on every fight but I don't see any dps saying I should sacrifice some dps for more survivability. Would it make turns like Turn 8, and Turn 9 easier on the healers if dps did this yes it would but almost every dps wouldn't want to lower their dps to make the healers job easier. You could do stuff like survive a double meteor stream without having a quick heal in there if all the dps had extra vit or survive a big aoe hit in T8 of heals were slow and everyone wasn't topped off in time. But the way the game is now people want the healers to do their job not give them more leeway to make mistakes.

Only some warrior tanks will use melded accessories because they want to sacrifice a little hp for slightly higher dps because they fell they can afford a lower HP and the healer can still heal them.