15 minutes per issue for eight hours (no accounting for breaks or time between) would be 32 issues. Per week. Even 40 hours a week is 160 groups, which seems pretty small given the size of the US.
Lobbying and staffers exist because the time of our representatives is really limited. I think it's a really awful solution, but I'm not surprised that it exists.
To make things more time efficient, you could even say than more than 5 people, with a designated spokesperson, can group together to block out an hour of time instead of making the representative hear the same issue the 5th time, and they have the benefit of being able to explain one subject in depth in an undivided manner.
Today we have the most amazing transportation and telecommuting technology available to perform duties in D.C., along with staffers to help. If representatives still can't make time for their constituency, maybe we ought to rethink their work division and responsibilities. Otherwise we run the risk of having presidents who don't know the price of milk.
No staffer-only meetings, the representative must sit through it and must fulfill a quota of X office hours per month, set according to their schedule. Each person / group gets 15-20 minutes. The hours can be cancelled up to 24 hours before for emergencies but must be made up within a week. How does that sound?
I get a bit mad when people suggest that representatives don't have time for that. That's their job, damnit! Make time.
This would really cut down the power of nepotism / cronyism in lobbying and bring politicians back down to earth, closer to the people they represent. Everyone should have equal access to their representative.