Mind Barrier + Shield Spell Block and Energy Shield on Shield passives not increasing ES correctly.

These 2 passives grant a combined 60% "Increased Energy Shield from Equipped Shield". My shield has 417 ES and these passives together increased my total ES by 250 (60% of 417).
My ring and belt have 15% "Increased Energy Shield from Body Armour" suffixes. My body armour has 626 ES and each one of these mods gives me roughly 450 total ES (15% of 626 = 93.9 with around 460% increased maximum ES modifier).

Meaning that even though they have identical descriptions, the gear bonus gives base ES, while the skill tree bonus gives flat ES.

I hope it wasn't intended this way and that I'm not incorrect with my observations and wasting your time.

Unfortunately that is how they are intended to function. (additive with other increases/decreases and not an increase to base value)