I play dark eldar and that's just mean.
It sounds like he is just bringing the direct counter to Tyranids. That's not a take all comers list.
I don't play the bugs myself but I can say that for fun you could tell him you are playing Tyranids then show up with an army of vehicles instead. All the poison weapons in the list can't touch any vehicle.
Venom's honestly die fast to pretty much anything, so if you can get first turn and shoot down a couple you might survive long enough to win..
But really there are certain matchups with
DE that struggle. Especially monster only lists. Not to mention
DE are really good at lower point levels because their maneuverability can keep them alive and their firepower against basic units is powerful. This is one of those bad matchups for you. Try the
FMC build and see if that works. Or try other opponents.
Also know your enemy, each venom is two hull points, ten armour, five up invulnerable save, and puts out twelve shots hitting on threes. On average that's eight hits and four wounds. Best of luck to ya