Scorching Ray Totems with the Fire Expore Mastery doesn't apply additional -5% fire res

So I tried using Scorching Ray with Spell Totem Support and the -5% fire exposure mastery and tested it with a friend in PVP.

Resistance did only go down by 25% on maximum stages.

When I removed the Spell Totem Support gem it worked and resistances went down by 30%.

So something is off with the Scorching Ray + Totems and the fire exposure mastery.

It's been bugged for who knows how long, GGG doesn't seem to care https://www.pathofexile.com/forum/view-thread/3187301