would it be dumb to get this box for thousand sons in 40k

Discount boxes for Horus Heresy are real it seems.

Astartes get 20 tacs, a HB/ML sprue, a Rhino and a leviathan. Which is kinda shit for spamming.

Admech get 6 thallax, 2 castellax and a Thanatar, 2 or 3 could be good but again bad for spamming.

The auxilia box is the best one by far for me at least, 1 command squad, 20 lasrifles, 2 light sentinels and a Russ. All of those units are extremely easy to spam in an aux army and you want A LOT of command squads.