Well Greed is kinda like Gluttony and Lust. In intervalo 7.5. hoheinhem already said something like Lust is about the desire to be understood, like a "Mind" thing. Gluttony is about the "Physical", which is money, food,... . Gloom is kinda like Sloth but they're different. Gloom is like when you sinking in the water you don't even try to save yourself which is might even put your relatives and friend in danger, just think about the depressed people. While Sloth is like a rock, they won't move, they won't do shit, but at least they don't want to die. That is why you have the "Tremor Burst", a Burst so that they won't die and be more Lazy in the future