Tim,
With containment mounding, there are also some issues of chems draining onto greens in bermuda surrounds/bent greens. My use of them is altered by that alone, plus as you say, getting tired of downhill lie chips from behind the green. Stopping a chip on a green falling away to the front is hard enough w/o having a downhill lie. Better a small swale and then a mound, if need be.
That said, one notable pro critiqued one of my back bunkers as too severe a downhill lie, saying it was a difficult shot for him. By that standard, the back bunkers would have to also be uphill shots, below the green, and thus blind on the approach, which I am generally loathe to do. Just seems like with the cost of bunkers, they ought to be seen!
Net, net, back bunkers for me are usually as cosmetic as anything, a relic of the old make it look harder than it plays by putting the same amount of bunkers in places unlikely to be found with golf shots, i.e., back left of the green.
So, what defines a "situation that really calls for it?"
I have a number of long par 4's with bunkers in back (and sides) of an across the LOP green, figuring, as you say, they test the long iron of the good player, who can still stop the long iron shot, but the handicap guy should have similar accuracy with third shot a wedge. I usually do these on prevailing up or downwind holes, not cross.
If the challenge is to make sure you take enough club (say uphill, into the wind) and the green front is open, then I feel the back bunkers create a little doubt about adding the extra club. Similar doubts might creep in downhill and downwind, too, encouraging the golfer to club to the front of the green, just to be sure they stay out of the bunker. Knowing that would leave a longer, but typically uphill put makes the "bail out" decision a bit tempting. In a prevailing crosswind, I don't see back bunkers having any similar effect.
At the same time, low handicappers, if you listen to Pelz, etc. have more distance control problems on short irons, so perhaps back bunkers make more sense for them on really, really short approaches, maybe the driveable par 4 or usually non reachable par 5?
For mid length holes, your scenario would kick in - good players always shooting at the flag with shorter clubs than the average guy, and probably being affected less.
Just my theoretical take. Of course, you start looking at what the land gives, the balance of the course, etc.