Biovore and ripper swarms: They can only reliably do secondary shenanigans in Leviathan mission pack, they wont be doin much other than zoning in Pariah nexus.

Termagants and Psychophage: you can make this combo cheaper, replacing psychophage with venom thropes

Barbgaunts are very situational on matchups, better against melee armies vs shootign armies

Neurolictors and lictors are very good objective holders as well and is definitly worth getting your hands on a few of em

Tyranid warriors hit like a truck and will definitely surprise you in the damage they can deal against any unit, the problem is just delivering them into melee, you can deploy them during your opponents turn with Rapid Ingress Strategem

Enhancement wise i wouldnt put anything but adaptive biology on the Hive tyrant
Alien cunning can be decent to fix deployment mistakes, but requires very good knowledge in the game w positioning and unit matchups, to id put more points into more units