I'm not sure I'm with your maths there. There's 2.3 million stones, divided by 30 years that's 76,667 blocks a year, divided by 365 days that's 210, so your 30 blocks an hour estimate is only a 7 hour working day.

The largest stones used in the construction are estimated at up to 80 tonnes, definitely not hundreds or thousands. There have been plenty of practical experiments with blocks that size using their known technology and it works fine, nevermind modern technology.