I agree with everything but the part where you said Gib and Caustic "shine" at close range. They actually do not. The 10% damage reduction means they have 220 effective hp+shield maximum. 20 more effective hp is NOTHING compared to how easier it is to dodge incoming projectiles with lifeline, wraith or octane.
Now let's see to kill Gib/Caustic if they wear purple armor:
- Eva-8 deals 56.7 damage instead of 63 => now takes 4 shots to kill (with ALL pellets landing) instead of 4 => NO CHANGE WHATSOEVER.
- PK deals 99 damage instead of 110 => now takes a 3rd shot to kill instead of just 2 => significant improvement but ONLY in the case where the PK user has 100% accuracy and Gib/Caustic are full hp/shield with purple/golden shield, in all other scenarios NOTHING CHANGED.
- R-301 deals 12.6 damage instead of 14 => now takes a max of 16 rounds instead of 15 => A SINGLE bullet more but considering how big they are and easier to land shots on, it is NOTHING.
- Flatline deals 14.4 damage instead of 16 => now takes 14 rounds to kill instead of 13 => A SINGLE bullet more which is insignificant for it's RoF.
- Hemlock deals 16.2 damage instead of 18 => now takes 13 rounds to kill instead of 12 => Insignificant yet again.
- Wingman deals 40.5 damage instead of 45 => now takes 5 rounds to kill instead of 5 => No change.
- G7 deals 27 damage instead of 30 => now takes 8 rounds to kill instead of 7 => Small change that is actually good because of it's lower RoF.
- LBow deals 49.5 damage instead of 55 => now takes 5 rounds to kill instead of 4 => Decent change that is actually good because of it's low RoF.
- TT deals deals 62.5 damage (when all 3 projectiles land) instead of 69 => now takes 4 shots to kill instead of 3 => Good change because it has a low RoF.
- etc.
I won't go through all as I don't want to waste all of my morning away but in short, the only weapons where this 10% damage reduction actually does anything significant is against sniper rifles. All automatic weapons shoot fast enough that taking one round more or less is insignificant so it does NOTHING to help against those. For Wingman and EVA-8 there is litterally NO change at all. For PK, the moment you do not land every single pellet with each shot or that the caustic/gib you are shooting isn't full hp/shield with purple/golden shield, there is also NO change at all.
TL.DR:
At short range and at medium range there is litterally nothing significant that was done to help them with their gigantic-extremely-hard-to-miss hitboxes. Only sniper rifles are really less effective because one more bullet to kill, considering their slow RoF, can make a significant difference.