Well, yeah, I'm driving a Disco, so low bumper, very high eyeballs. I haven't exerienced this *yet* in the truck because I haven't done much with it yet. But I have in my cars.
My track Focus has Hella projector lamps for headlights with 100W bulbs. Quite bright. And I get this effect to a certain degree but not too bad.
I used to have another daily driver Focus, with Hella FF1000's mounted at exactly bumper height (so under the factory headlights) and this effect was really quite bad. It almost made it pointless to use the driving lights on anything other than completely flat roads.
Previous to that, I had the FF1000's mounted to my wife's Focus on a mounting bar that positioned them over the line of the headlights, and these were the best I ever had by far.
It would seem to me that having lights on the roof, projecting down in front of the vehicle would be really help throw light down into the holes so you could see what's really in them.
You're right, in that you can't see anything out of your line of sight anyway. But my point is, any time your lights are lower than your eyeballs, you're giving up the potential to see into holes.
Maybe this effect isn't so big on something like a Taco. But on a Disco, your eyeballs are very high indeed. At the very least, you'd want you aux lights mounted *on top* of your bullbar, but that would look just as "bubba" as having them on the roof anyway.
As a sidenote, has anybody ever done anything like putting small projector fogs somewhere... like under the rear view mirros, so light the ground to the side? Or where is the best/most common place for this? Rack again?
Enduro motorcycles who have to run at night are putting small projector lights right onto their suspension forks aimed at the ground right in front of the wheel. In addition to their headlights, and then also two projectors on the sides of their helmets to light up where they're looking. It's all about putting light where you need it even if it looks silly.
Baja bikes just you the big lights on the front, because they need to light up a ways into the distance. By the time any obstacle is close to your wheel, it's too late to do anything about it at speed. In a slow slogging enduro you need light closer in, and you need to put it where you're looking.