I do agree with you that the luck should be change to make 3v2 reliable enough to depend on when 1 of them are required. One thing I like to do is take a bonus with 4 other territories, attack 2 of them using 4 armies usually yielding one stack of 3 and another stack of 2 so I can then use them to do 2 more 4v2s to take the bonus. In this game:
http://warlight.net/MultiPlayer?GameID=6678474 (I am still a little frustrated by this so forgive me)that same strat yielded me 2 stacks of 2, and as I wanted to continue trying to get SA I did a 4v2 attack and a 3v2 attack and then it was game over with a net luck of -1.7 in 3 turns
While this was on the real time ladder, the same concept still applies, luck should not completely determine the winner.