Do they say anything about what classifies as a "spam army"? Without any guidelines, that feels like a pretty ambiguous statement. I'd definitely call or e-mail and ask them to specify a bit on what they mean.
Edit: To add some input, if you're restricted in the amount of venoms/raiders you can take, I'd consider fielding large blobs of Kabalite warriors to hold backfield objectives with a pair of blasters and dark lances, maybe. If they are sitting in ruins, they are pretty hardy in large numbers. I'd imagine fielding x3 Ravagers would be considered "spammy", so it helps with your deployment area coverage.