These aren't just "nuns with knives." A lot of companies have taken their own shot at that. These are sculpted in the exact same style as the GW figures, and are covered with cliche Sigmarite symbols. In fact, they arguably align with three specific characters from Mordheim.
Honestly, if they had even just left off the comets & lettering, I would have given them a pass on the "close but still generic enough."
Regardless, if GW it sitting on their IP, that's their business. They may have other plans for it, and it's their right to let a game sit idle for a while. They let Space Hulk go dormant for years at a time, but have brought it back. It doesn't give third parties the right to rip them off. The fact that not everyone has access to the old figures or can't afford the prices they fetch on the secondary market doesn't change that.
Believe me, I am far from GW's biggest fan. I buy figures from a bunch of different sources. The same IP laws that protect GW also (theoretically) protect small & independent companies that develop their own IP.