Having been involved in the open national comps at Lasham a couple of weeks ago where we were set tasks over 650kms the areas of countryside covered with bloody hard to see gliders can be pretty staggering.
As to the level of lookout kept by glider drivers, it's actually very high, especially in thermals.
When you are in a gaggle with up to 40 other gliders all spinning in their own variations of a circle and vertical separation in the tens of feet between you and the next 750kg of plastic doing 55kts self preservation dictates that you activley participate in the 3D version of "asteroids" you find yourself in.
The VSI main output is audio, the analouge display is there really just for decoration.
Nav in a staright line is handled pretty much automatically by computers these days so that doesn't take much "head down" to follow.
We are _always_ looking for other gliders / ac you literally have a sore neck after a 6-8 hour comp flight.
Do have to agree that we are _very_ difficult to see from any distance away.
Don't know how to improve that situation though.