Earlier quoted context omitted.
With 535 of them not including staff, they really shouldn't. And clearance isn't enough, you also have to have a need to know. We just need a system of oversight that works well.
With the amount of NSA staffers and people who have clearance being well above that number, really?
NSA staffers have defined roles and are given information on a need-to-know basis. Obviously the Snowden leaks proved that at least for a sysad, the technical component of the need-to-know restriction was broken, but that's how it's supposed to work.
For Congressional oversight to be useful, Congress (or a subset) need a higher level of access than that given to the NSA themselves - the ability to ask for any information and have it given to them.
That's a pretty powerful tool, so I don't think the "well NSA has lot of people" counter is valid.