Previously, level 112 spell: Protest for Honor had the chance to proc a slow on undead NPCs: Helix of the Undying. The current iteration of this spell, level 117 spell: Parlay for Honor is not procing any sort of updated Helix spell.
From an AA you need to purchase or didn't get a ToL upgrade? There's no slow in the spell data. Against what mobs because a lot of typical undead mobs seem like they might not be flagged undead in ToL.
Good questions - I may be mistaken. Looks like under AA > Focus > Improved Demand for Honor, there is in fact a new ToL tier that I do not have. I wasn't sure on how this worked ever since the actual slow AA was removed many years ago and tied to this spell instead. Now I know better! No bug here it seems.