I must say this box is very poorly composed, I think it's more of a "these models don't sell as much", let's throw them all into a box with a discount.
The reason they don't sell are obvious, they are bad options (competitively & narratively) or you get very little bang for your buck.
Wraithknight was under-costed, but is now over-costed, so "everyone" that wanted one bought them when they were still good.
Vypers has been bad since the times when they could block access ports for passagers.
Windriders are just like the wraithknight, was good, but is now not only over-costed, they are no longer troops, in addition you get very few points worth for your money.
Dire Avengers are ok but not really kicking it and just like the windriders very little bang for the buck.
Farseer, where is his ride, no skyrunner nor wave serpent, a farseer/warlock on bike would have been a better pick.
Guardians, is the only thing fine in this box IMHO.
I can understand why they wouldn't want any metal or rubber models in the box, but having a Wave Serpent, a unit of 5 wraithguard/blade and a bike-psyker rather than the Knight, Vyper & Seer, wouldn't be too much to ask, if you ask me.
I would say rangers over windriders too, but rangers are still metal afaik.