What Hive Fleet are your Nidz?
Anyway, a general recommendation is to take a unit of Venomthrope, that -1 to hit is huge. I am not So sure If the Haruspex is good or just a waste of points, but I see the good units in your army is Genestealers, Hive Guard and Exocrines.
Maybe you will want to build your army in two portions, the 1st one being a horde of Genestealer (to eat any enemy they touch) and a unit of Hormagants (used to tie up enemy shooting units). Under the cover of Venomthrope, these units should be able to overwhelm enemy firepower, leaving enough of the little bugs wreck havoc in enemy line. Especially the Genestealers If you use Kraken Fleet, they are supersonic. Meanwhile the 2nd portion of your army would be a large brood of Hive Guard, and some Exocrines, they can shoot anything that is not an Imperial Knight or buffed by Aeldrai trickery to pieces.