As a matter of clarification, I do run digressive valving front and rear. When I drive I keep the dampening low. But I had it in the middle setting when the accident occurred.The lack of swaybar is not the cause of the issues you later cited, but the fact that you prefer low damping as well. And it isn't just high damping but a digressive curve that adds stability. My truck handles better than it did previously with stock shocks and the swaybar, and if it's also a rough road, the improvement is amazing.
I agree that digressive valving and higher dampening can really help keep things stable. But to someone who has no experience driving a vehicle without sway bars (especially a vehicle that is much taller and larger than what they are used to), things can go south in a hurry.
I'll also add that alignment can play a part in this as well. On my truck in particular, increasing the caster to much higher than factory specs helps with stability significantly.