Master Toxicist not working with Withertouch mercenary

I'm playing Viper Strike of the Mamba, and while using a Withertouch mercenary, the poison proliferation from Master Toxicist from the Pathfinder ascendency doesn't work.

The mercenary I used has Bane, Temporal chains, Altar of Chaos, Essence Drain of Wickedness, Malevolence, and Lightning Warp.

The mercenary didn't have any gems or items with a chance to poison that would have made Viper Strike Mamba not work.

I've also noticed some wonky behaviour with this guy.

Anyone else have the same issues?

Yeah.
From my testing the curse that causes the most problems is Temporal Chains.
Doesnt matter if it’s mercenary’s skill or trigger from gear.

Oh, also forgot to mention - it’s not just Withertouch mercenary - it applies to any merc casting a curse

Was also reported here: https://www.pathofexile.com/forum/view-thread/3799544

/bump

Same issue here

Has this been fixed?