Except what you fail to take into account with this is the fact that numbers DO matter, 17 people to 15 may mean that while in a rough 5/5/5 split for Aggressive, Defensive and Field Support, a 2 player addition to any of the groups, would be a massive swing in their favor. 7 Medium skill tank players vs 5 High skill tankers, numbers make a massive difference. (Bare in mind this is just an example) but this is something you need to take into consideration.