Did you know? The game itself often does a relatively poor job of correctly representing skill damage, especially when using secondary skill mechanics.
This also applies to this build. For example, the DPS indication (white text on the top right) you get when you hover over your (G) Toxic Rain skill is completely meaningless, as it represents the physical damage of the skill. However, this build scales chaos damage, which is not even considered in this value.
To get information directly in the game about whether changes to items or gems reduce or increase your damage, you need to look at the value that is in the blue text, specifically the value ‚Deals X Chaos Damage Per Second‘.
But even this value is only an indicator. If you want to know the real damage values, you have to resort to third party tools like Path of Building.