Just remember that you still need to hit with Psychic Shriek, which means the Tervigon's average BS hampers its use. Mind you though, it is nearly always worth it.
I find Hive Guard are still more useful against most vehicles you will see, especially considering they ignore night fighting, jink, smoke launchers, etc. There's virtually no way for a vehicle to get cover from Hive Guard.
Mind you though, Zoanthropes are my favourites and always have been.