[2020] How come GGG nerfed Herald of Agony Virulence stacking mid-league, but won't nerf Purposeful Harbinger until next league?

With Lone messenger and Pure agony you could reach more than 100 Virulence stacks for HOA because it had multiplicative interaction with buff effect. Bex posted earlier, that by nerfing Purposeful harbinger it would ruin too many people's builds. So screw HOA players, right?

Mid-league changes should be universal for all builds. Either don't change anything after the league release or do a balance patch after a month or so for everything.

What then should I expect in future leagues? I have no idea if I should invest in an OP build because it may or may not get nerfed.

Maybe finally hire playtesters who can make it past Brutus.

EDIT: To make it clear, my issue isn't the aura build itself, but the fact, that nerfs happen unpredictably. GGG should be more transparent about mid-league changes in the future.

EDIT2: While it may be argued that one was a bug and another just OP mechanic, how is a player for the purposes of investing in a build supposed to know if auras affecting Black Cane, Solstice Vigil, Sporeguard, Tailwind boots or even golems are intended?

EDIT3: Consider this happened few leagues ago https://www.pathofexile.com/forum/view-thread/2051270/page/1 - that was 11 days after the league release.