the threshold did change relative to the xp spent on damage by the other team. i guess that is what people mean but that seems rather tenuous to me.
Yes, that's exactly what's meant.
Before, you needed X amount of XP sunk into GA to counter a certain ranged weapon, DD or melee weapon.
After the damage rescale, you only needed X*0.66 to fully punish the same ranged weapon or enemy DD and only X*0.44 to fully punish the same melee weapon.
...and that when DM/RoS is not at all involved.
When DM or RoS is involved, it might very well be the difference between almost no damage returned to almost full damage returned for the exact same previous situation.
So, yeah, GA should have received some degree of "nerfing" alongside the damage rescale, anything between *0.66 to *0.5 effectiveness (+50% to +100% XP needed for same end effect compared to the CURRENT post-damage-rescale situation).