As I understand it, more recent Time Capsules took out the SNMP functionality that would allow me to monitor bandwidth usage to see what device(s) were gobbling up bandwidth on my network. Is there a way to do this, despite that limitation?
It wouldn't show you what exact device is wasting your bandwidth anyway.
You just could see the aggregated b/w usage of your wireless (separately on 5 and 2.4GHz), your LAN ports (3 of them on Apple device), and your WAN port. If you bridge your AirPort, all 4 Eth ports consolidate under LAN port and WAN port will show no b/w usage at all.