It sounds like you don't really understand the meaning of these settings. Have a look at the WL wiki pages for [combat](http://wiki.warlight.net/index.php/Combat_Basics
) and [luck](http://wiki.warlight.net/index.php/Luck_Modifier
), they explain how things work.
Very, very short version:
60% offence luck means each attacking army has 60% chance of killing a defender.
70% defence luck means each defending army has 70% chance of killing an attacker.
Of course the game favours the player with most armies; it wouldn't make sense to favour fewer armies...!? But, to have a sure, easy victory, you need a **large** number of armies.
0% luck -> just calculate (10 attackers, 60% offence luck = 6 defenders killed, always)
100% luck -> simulate dice throws (10 attackers, 60% offence luck = between 0 and 10 defenders killed, with an [expected value](http://en.wikipedia.org/wiki/Expected_value
) of 6)
Other luck modifiers are simply a linear interpolation of these.