You've got the makings of a fairly solid list here. Some suggestions on how you could improve it (while respecting your unit choices, so I won''t suggest "3 x Flyrant"
)
* First of all, I'd split up the Venomthropes in 3 individual units. While this will leave you more vulnerable to kill points, it will also allow you to spread out your Shrouding and forces your opponent to dedicate multiple units to take them all out (some armies have so much firepower they could conceivably wipe out an entire shrouded Venomthrope unit).
* Same remark for the Zoanthropes, split them up. As an added bonus, you'll get 2 extra Warp Dice this way!
* Your Hive Tyrant is fine, but I'd add Electroshock Grubs, just because they're so good.
* This may be a personal preference, but I'd remove the Adrenal Glands from the Hormagaunts. Horma's are meant to be fast cannon fodder and adding Adrenals to them makes them too expensive for my taste.
* Your 'hidden' Devourer gaunts are a good idea, but 16 is a bit much, chances are you won't be able to bring them all into play. I'd drop them to 11-12, which is still respectable firepower.
* The saved points will allow you to add electroschock grubs to your Tervigon, and also to add a Tyrrannocyte (if you have one). Depending on the opponent you can then put the Devourergaunts or the Claws/Grubs Tervigon (or even the Carnifex) in it, and drop it in the opponent's backfield.
This would give you approx. this list:
COMBINED ARMS DETACHMENT
HQ:
Hive Tyrant, 2 x Devourers, Wings, Electroshock Grubs
Elite
Zoanthrope
Zoanthrope
Troops
Tervigon, Crushing Claws, Electroshock Grubs
30 Termagaunts, 12 x Devourer
Heavy Support
Tyrranocyte
COMBINED ARMS DETACHMENT
HQ
Tervigon, Crushing Claws
Elites
Venomthrope
Venomthrope
Venomthrope
Troops
20 Hormagaunts
20 Hormagaunts
Heavy Support
Carnifex, 2 x Devourers
Good luck!