Advanced Basilisk is by no means useless. I'd consider it an incredibly great solo hunter. Using the alien sensing humans ability, it's great to sneak up and track humans, hoping that they'll stray far enough away from the group that you can sit on their head for 2-3 seconds before their buddy saves him. The gas is pretty damn useless, but those 25 extra hitpoints are to die for. But yeah, admittedly, b-suits do trash the basilisk. But that's just like saying advanced goons trash the pain saw. Both painsaws and basilisks are great S1 and S2 tools, but lose their effectiveness against S3 opponents, and fully rightfully so.