On most highways in WV, the maximum speed limit is 70 MPH and the minimum speed limit is 45 MPH. The law is, turn on your flashers when travelling at less than the minimum speed limit.
One flaw in your argument concerning turn signals is that under the conditions you describe, nobody should be changing lanes. Lane changing when you can't see is dangerous and little flashing lights aren't going to improve your ability to see one whit.
Pulling over to the shoulder to wait out the hazardous conditions is always preferable when it can be safely done, but if you must press on, then slow down enough that you don't overdrive your visibility. If you leave enough gap between you and the vehicle in front of you, you are not going to rear-end them regardless of whatever maneuver they may perform.
The recent pile up near Fancy Gap Mountain in Virginia was not caused by the use of flashers, but by people driving too fast and following too close for conditions.