Idea for SameTime Risk battles:

Instead of rolling D6s repeatedly until only one force remains - which can, for example, result in an army of 3 beating an army of 15 - just have each force roll a 'luck modifier' at the beginning of the battle (A D6 each; if one army is clearly a 'defender' while others are 'attackers,' have the defender roll a D6 while the attackers roll D4). The force with the lowest (armies + luck modifier) is knocked out, with their (armies + luck modifier) subtracted from the other forces army sizes.

This means that a force of 8 is always guaranteed to beat a force of 1, but if the troop numbers are any closer together then it's uncertain: a troop of 1 has a 1/36 chance of beating a troop of 6.