OK, stat time.
CarnifexCode:
AV 20cm 4+ 3+ 5+ Brood, Fearless, Reinforced Armour
Bio-plasma (15cm) Small Arms -
Large Scything Talons (base contact) Assault Weapons Extra Attack (+1), Macro-weapon
Zombo and I talked about the move and I'm going to go with 20cm here given that you can make them faster in 40k5e and they were faster in 2e. So just try and ignore all the stuff that came between that

. They've gone to 4+RA to be on par with the Tyrant.
Devourer CarnifexCode:
AV 20cm 4+ 4+ 3+ Brood, Fearless, Reinforced Armour
2x Twin Devourer 15cm AP3+
Let me know if I got these right Zombo.
Barbed CarnifexCode:
AV 20cm 4+ 5+ 4+ Brood, Fearless, Reinforced Armour
Heavy Venom Cannon 30cm AP4+/AT5+ -
Stranglethorn Cannon 30cm AP4+ Disrupt
These too.
Onachus ZoanthropeCode:
LV 15cm 4+ 6+ 5+ Brood, Invulnerable Save
Warp Blast 30cm AP5+ -
and (15cm) Small Arms Macro-weapon
Its save was changed to reflect its invulnerable save in 40k and how close it's close to a SM Attack bike in 40k stat-wise. The Warp Blast was given a 30cm shot as it was fairly long ranged in SM/TL and it's an assault 24" weapon in 40k, rather than a rapid fire or heavy (so it was bumped from the usually 15cm). The FF stayed as it, as its warp lance is close to what a multi-melta (FF5+MW) is in 40k.
Leviathan ZoanthropeCode:
LV 15cm 4+ 6+ 5+ Invulnerable Save, Jump Pack, Invulnerable Save
Warp Blast 30cm AP5+ -
and (15cm) Small Arms Macro-weapon
Pretty much the same as the Onachus version, just with Synapse instead of Brood. It was given Jump Pack to represent the floating. Yes, it doesn't float high but it can still float over things like lava and rivers.
VenomthropeCode:
LV 15cm 6+ 4+ - Brood, Jump Pack, (see below)
Toxic Miasma (base contact) Assault Weapons Ignore Cover
Notes: Up to two friendly light vehicle or infantry units in base to base contact with the Venomthrope, and the Venomthrope itself, may claim a 5+ cover save and the -1 to hit modifier for being in cover (see EA 1.8.3).
The above stats are an attempt to make them more then just another CC beast. With them being classed as LVs a unit note would have been needed anyway to have them count as AVs to grant INF concealment so I just took it to the next level: they are mobile cover. Definitely something that will need testing but it also makes them pretty unique.
BiovoreCode:
LV 15cm 6+ 6+ 5+ Brood
Spore Mines 30cm AP5+/AT6+ Disrupt, Indirect Fire
These saw an armor decrease to reflect their 40k-stats and a FF increase as their shot is the equivalent of a multi-laser in EA (FF5+). Disrupt is staying as it just "feels right" plus I didn't see any objections to it.
PyrovoreCode:
LV 15cm 6+ 5+ 5+ Brood
Flamespurt 15cm AP4+ Ignore Cover
and (15cm) Small Arms Ignore Cover
Same stats as the Biovore but with a CC increase to reflect their acid-maw and a weapon swap.