Is this still relevant? Most daemons gain an insignificant amount of TB, which bolts seem entirely wasted and sanctified weapons are just a bit meh currently.

Based on the effects of fields PC's wield later on would it be better to change it to field save, which is more reminiscent of the TT? Daemonic 5 (giving a 50% immunity although you'd only need to roll 1D10 if we aren't worrying about overload) would be the basic for most Daemons, Tzeentch daemons would have Daemonic 7, Mark of Tzeentch follows get Daemonic 3.

While I am an avid player of TT, I'm not quite as familiar with the DW rules. But I see no problems with this. And it helps against PCs at higher levels, where their shields turn everything into alpha strike scenarios.