Thousand sons list seems alright, I'm not a huge fan of massive tanks so I tend to go for obliterators though.
The Herald in the deamon list is too fragile on a chariot, it's too easy to kill it. You'd be much better hiding him in a horror unit with the loci, it would up all the pink horrors shooting attacks to S6, as well as prescience from divination. Hide these behind an ADL and you get a solid save, as well as a re-rerollable 2+ cover if you go to ground!
'If you fail to prepare then you'd better prepare to fail'