You are correct in thinking 10 avoid is a bit deal thats another 1 in 10 less chance of being hit for each avoid skill plus however much you stack in speed and luck. I was thinking of doing an avoid stack myself. it seems super viable, however if your going for a more risk based strategy like avoid you may as well go with a vantage crit spam, killing anyone before they even attack seems as good as never being hit, especially on street pass teams.