here are some things I have experienced, learned, and read about (and confirmed) having gone through so many, many boots:
I don't understand wagga and bee
your tying method "low" means the ankle is not the job of "holding" the rest of the foot from sliding forward in the boot. I always tighten up the top 2-3 rows even more for downhill to prevent black toe syndrome
Low-toppers are more risk for black-toe syndrome than high-toppers. They obviously cannot grip the ankle.
get a boot a half size larger than what you think. Most shoe places don't even fit you right. Put on the shoes/boots, lace them up, stand, lift one foot up behind you, then point the toe end down and whack the toe-end on the floor. Even with the whacking, the toes should not "bottom out" inside the toe-end of the shoe. Toe-box should be big enough to prevent that, and ankle-lacing should be tight enough to prevent movement.
another factor- sweat. allows slipperiness inside the boot and thus allowing foot to slide forward on downhill. Thin liner socks under thick wool works well for blister prevention and wicking sweat away. You could even spray antiperspirant all over your feet if the slipperiness is a major factor.
