Which NSX feature would enhance their security so that this doesn't happen again?

NSX enhance logical switching, load balancing and microsegmentation which improves networking performance and operations.

The performance starts in Layer 2, NSX manage routing even in virtual or cloud networks. Its firewall can support up to 20Gb traffic and monitoring all at once. Next work will in Layer 4 to 7, using SSL by making regular routine checks on network activities on this layer.

As for security features, it uses microsegmentation which can make administrators manage policies of the network including making security groups. This would prevent previous attacks to happen again because NSX has firewalls that records and set policies in a network.