Nice guide, however seems a little slow. The over 3:00 will be painful in the long run, especially as it seems zulrah's drop rate is modified to be higher.
Currently I've been experimenting, and by using dbow with full armadyl range, and rune darts to kill snakelings, I'm getting about 2:00 times. I'll keep ya posted on faster methods I come across, but by far this one is the fastest.