Ann: Thick Intercept in Deeper Drilling of Conductors, page-95

I dont believe that drilling at depth is necessarily more hit and miss.
It depends on the type of rock being drilled, the angle of the hole, the pressure being applied to the (drill) bit, whether they are drilling "good rock" or fractured rock, a shear zone etc.
The experience of the driller can use all of these tools to keep the hole on target as the hole progresses. Some rocks can be drilled flat out with relatively no deviation of the rod line. Sometimes even just a change in speed of rotation can change the direction.
Some rocks can have more pressure applied to "bend" or deflect the rod line across due to the rotation of the rod line or even up if necessary.
Some rocks will respond to decreasing the pressure on the bit to allow the rod line to "fall" depending on the relative angle or the increasing length of the rod line and the hole etc. Simply the increasing weight of the rod line or the type of matrix of the bit can also influence characteristics as well.
Some geologists would expect the driller to get within a metre or two of their "target" at one to two thousand metres down! I used to say that if the target was that small it wasn't worth getting anyway.......ha ha.
Its a fascinating game that's for sure.