Well one question, what points limit is this at?
On another note, maybe this kind of group might work. I know this has worked for some people as a general build.
(240) Hive Tyrant, 2 TL-devourers, armored shell (armored shell isn't always taken, but I see it in a decent number of lists)
(60) Tyrant Guard
(100) Tyranid Prime, boneswords, regenerate -he uses look out sir! to allocate wounds, and to absorb wounds himself (and regenerate them hopefully).
(195) Tervigon, AG, TS, catalyst
(195) Tervigon, AG, TS, catalyst
(50) 10 Termagants
(50) 10 Termagants
(100) 2 Hive Guard
(100) 2 Hive Guard
(380) 2 Carnifexes, 4 TL-devourers -maybe as two squads, but catalyst affects a unit, so having them together makes them both get FNP
This is 1470pts, and would scale nicely proably to 1750/1850 if you needed it to. Add some more heavy support, and/or some stealers maybe (this isn't my list, but a template I've seen on a lot of lists)
Generally you keep the units clumped up, not necessarily in cover, though the tervigons should be further back. The strategy I would employ would be to allow the venoms to approach you (to get within range).
Try and get catalyst off on at least the tyrant or the carnifex brood. This will give your opponent their first negative incentive scheme: shoot the tervigons that don't directly threaten their venoms.
-tervigons will be behind the MC's+termagants.
-venoms will have to get way in range of the other tyrant, fexes, and hive guard in order to kill the tervigons.
-either way, you can move 6" and get in range of venoms when they come for you.
Once the venoms get within range, you can unload the fexes, tyrant, and guards. On average, just the tyrant's shooting should down one venom that has 5+ cover (they only have 2HP). The fexes should overkill one venom, and the hive guard together should kill 1-2 venoms depending on your luck.
If all goes according to plan, he should fail to kill more than 2 of your groups (tyrant, fexes, or both hive guard units) since you have lots of wounds and a prime as a unit that can throw wounds all around models.
Lastly, if it is a 1850pt game....I'm not sure this would work either, but you could maybe grab 2 venom cannon harpies... its 340pts for both of them, and they could possibly remove the war walkers, leaving the ravagers to be dealt with.