With 1.75, I can answer your question. However if you are playing with 1.74, then there will be unsatisfactory answer.
Playing with 1.75:
Play with a stack of your units that can "Hunt". Then go into BUG option and go to Automation page. Go down to Hunt section and adapt odds that the units will generally attack or above. Then click on Suiciding units. The mathematical aspect of suiciding odds is this ATTACK! = (Odds you set in there) divided by (total units in the stack hunting. So if you have 5 warriors (for example), and set Hunting Odds at 50%, then normally they will only attack with 50% or better odds. But with suiciding units on, you will expect to see weakest warrior of 5 to attack at 10% or better odds.
For 1.74:
Afforess set Hunt's odds in C++, and I don't know the exact odds. I'm assuming here: 70% maybe. So that make it hard for units in 1.74 to attack if auto hunting.
See why I love 1.75 AUA incarnations
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