Kyle,
I never thought it was yardage markers that reduced nasty back bunkers. I thought it was the desire for visibility. Hard to have a deep back bunker when it has to set above the green to be seen, as you state in your last sentence.
The other side is how most of us route holes - with greens set in gentle up slopes, which make deep back bunkers rare. If a green is on a downslope, they tend to be deeper naturally, although most back hazards below the greens would be grass. Given the cost of bunkers (liner, drainage, perfect sand) it does seem a shame to build one where no one will see it. And the grass bunker is just as tough.