"The Tormented" (i.e. Daemon Prince + 2 units of Possessed WS5, I5, S5 and Rending) seems to be a "Black Legion" formation (so, without the "Slaves to the Voices" table, but the usual "Vessels of Chaos" one). These would remain the closest Possessed to the ForgeWorld Gal Vorbak of HH.
The new "Crimson Slaughter" seems to have a "Dark Covenant" formation, with one unit of Possessed getting "Zealot" (i.e. with "Hatred") and "Feel no Pain !" when in 12'' of a Dark Apostle who is shouting instead of shooting. That could be interesting too, with 1-3 Space Marines units getting the same bonuses.
I play Word Bearers too, on a fluffy base coming from BL HH books (principally "The First Heretic"), and Possessed (Gal Vorbak inheritance) are the first unit I put in every list. The best results I've had with them is with the "Crimson Slaughter" ones : marked by Slaanesh, with an Icon of Excess and a (unaligned, with Malefic Daemonology) Possessed Sorcerer joining.
What I would like to try up next : two units of Possessed, one marked by Khorne, the other by Slaanesh and a Landraider. That gives me 1/3 chances for each unit for the first turn to be able to make their transport "Shrouded". If it is the case, that unit moves into the Landraider, which moves on 12'' and uses smoke launchers for a 3+ cover save at first turn (being in charge range at second turn, with a well-placed Dirge Caster and, maybe, Destroyer Blades too). But it costs a lot ;)