Plague bearers (no more going to ground) 5+ FNP
plaguebearers did get the FnP reduction up the ass at first glance, but they now get it against more things, and it's all the sweeter when you get epidemius's tally up for the 3+. they can also take chaos marines as allies to make this easier with shooting capabilities. as for going to ground, why would you? they are a tarpit, and making them unable to assault or attack back is doing it wrong.
the most major buff i have seen is that sanguinary guard NO LONGER SUCK!!! the 2+ armour and PW changes means that they wont die easily to some weaboo sergeant with a power weapon, and jump packs are even better now. also, feel no pain has the ability to make them pseudo flying terminators unless they are getting shot with S8+.
mephiston is still aweshum, as even though fleet isnt as great, and he is only AP3 (cant they just make him an MC?(please)), psychic powers got amazing, and having no invuln isnt as important when a 2+ armour is so much better. and hes T6 with 5 wounds, which he has a 33% chance of being able to regenerate if he rolls 3 times on biomancy-and you had better do that, cuz mephiston+iron arm, warp speed, and life leech=OMFGWTFBBQPWNED
as for nerfs...
death company dreadnoughts arent as great, because ignoring shakens and stuns doesnt matter much when glances don't inflict them, and instead rip you apart.