What model is this, that represents Enslavers?
That pic/those models first appeared on BoS back in 2007 under the &quot;Warhammer 30,000 League – Week 3&quot; report. Other pictures in that report also show those figures.

With the description:

Balkus
Alpha Legion, Enslavers
The Alpha Legion under the command of Master Arkos, scored a hard fought victory for the Imperium upon the lost empire of Balkus. With its fate unknown for over 5000 years, the vile warp-spawned Enslavers have been cast out of this world forever. Captain Arkos has yet again done a service for the Imperium!
World Status: Compliance

The White Dwarf article in your link is apparently the only source for those rules. The models in the picture seem to have been original/custom.