I only use the 3-stat potions as well. I have an auto-loot filter that auto-junks any potions I find (among other things) and I either sell them all off (along with everything else in my junk folder)…
No reason to put any points in it at the moment. If I had to speculate I would guess that this passive may get a makeover and become useful when poisons are introduced.
As stated above, this passive isn't about reducing effects of others' potions on you; it's about reducing negative effects of potions you drink. It's too easy to make potions without negative effects…