How does Tuna Party stacking work?

Do the shields just stack on top of each other? Doesn't that make lvl 1 spam with 2 Cute Grass Necklace better than ever casting level 5?

Also it doesn't seem to block EQ damage, but that's expected really. So is Stoop an effective way to deal with it?

It doesn't stack, it's just a graphical bug that will never be fixed. It happens when you cast tuna party on a target that already has the buff.

It does block EQ damage but some MVPs like ifrit have an incredibly painful EQ. Tuna party also doesn't block the reduced damage from skills like stoop and mental strength, even with these skills active, the shield will still take damage as it would have if those skills were not active.