So get more TAs. They cost less than Class B CDL drivers and will drag themselves over broken glass to take these jobs. And 65 hours of work per semester for oral examinations seems entirely reasonable. A week and a half for an FTE spent observing, with another half week to full week for grading seems completely reasonable for capstone semester work.
Hiring a n TA to delegate grading that’s hard to verify seems like will cost more than you think.