The extensive channel sampling in conjunction with the tunneling done to date is giving us an excellent geological picture. This is very hilly country, so channeling and cross channeling at different levels as well as the tunnel sampling, ARE giving us an indication of potential depth This gold did not fall from the sky. It came from beneath. Anybody that pooh-poohs channel sampling does not know what they are talking about.
T2's calculations are probably closer to the truth than many believe, but until Batoto is comletely drilled, we can only speak of this world class find in hushed whispers. (IMO)