Well, there is some difference between 318 and 1,500 students, but that is unarguably too many for four non-Wikipedian CAs to handle. Too many for four Wikipedians to have handled, too, for that matter.
I'm not sure I follow your logic on the grad student bit, though. Don't get me wrong, being paid for my CA work would be great. However, paying grad students to do the work? Unless you're specifically talking about finding grad students who are also Wikipedians, it seems like you'll have the same issue. Paid or not, they're still not Wikipedians. I don't think the current issue with the CAs is that they don't have a monetary incentive to do the work. They just aren't familiar enough with Wikipedia to know how to handle some situations. Paying people who don't know Wikipedia will not change this.