Game mechanics question: firing in stacks?

[Glenn Saunders]

Right - and I thought of another and it opens a can or worms too - that is ASSAULTING - I often perfer a couple good odds ASSAULTs over ONE VERY GOOD Assault - just more chance of success I find. But the assault is a Atatcker vs Defender Strength and so it is much different from firing which is Attacked vs a Defense factor